As sugested, I have just now downloaded the notepad++ Zip package to my desktop system, extracted the files to a folder on the desktop and run the .exe and I get the same problem that I reported before. I have done that with both the 64bit and 32bit versions of notepad++, both show the same incorrect behaviour. I then checked notepad++ running on an Asus laptop computer, also with Windows 10, and the problem does not appear on that machine. So I guess the problem only occurs with some Windows 10 systems.

With the desktop machine, I find that the problem does not occur if instead of clicking on Cut, Copy and Paste with the mouse I use the keyboard combinations ‘Ctl X’, ‘Ctl C’, ‘Ctl V’ so for me the answer for the time being at least is to use those keyboard combinations instead of the mouse.

I dont know of anything unusual about my desktop computer which is working fine for all my other software. It does have two 2560x1600 pixel monitors connected to a single graphics card, but that has not been a problem with other software. I dont know if it helps but this is the system information summary, including for the display:

System Information report written at: 12/21/19 15:38:12
System Name: DESKTOP-UGQ9O4I
[System Summary]

Item Value
OS Name Microsoft Windows 10 Home
Version 10.0.18362 Build 18362
Other OS Description Not Available
OS Manufacturer Microsoft Corporation
System Name DESKTOP-UGQ9O4I
System Manufacturer ASUS
System Model All Series
System Type x64-based PC
System SKU All
Processor Intel® Core™ i7-4790K CPU @ 4.00GHz, 4001 Mhz, 4 Core(s), 8 Logical Processor(s)
BIOS Version/Date American Megatrends Inc. 2902, 31/03/2016
SMBIOS Version 2.8
Embedded Controller Version 255.255
BIOS Mode UEFI
BaseBoard Manufacturer ASUSTeK COMPUTER INC.
BaseBoard Product Z97-K
BaseBoard Version Rev X.0x
Platform Role Desktop
Secure Boot State On
PCR7 Configuration Binding Not Possible
Windows Directory C:\WINDOWS
System Directory C:\WINDOWS\system32
Boot Device \Device\HarddiskVolume2
Locale United Kingdom
Hardware Abstraction Layer Version = “10.0.18362.387”
Username DESKTOP-UGQ9O4I\John_local
Time Zone GMT Standard Time
Installed Physical Memory (RAM) 16.0 GB
Total Physical Memory 15.9 GB
Available Physical Memory 9.66 GB
Total Virtual Memory 18.3 GB
Available Virtual Memory 10.4 GB
Page File Space 2.38 GB
Page File C:\pagefile.sys
Kernel DMA Protection Off
Virtualisation-based security Not enabled
Device Encryption Support Reasons for failed automatic device encryption: TPM is not usable, PCR7 binding is not supported, Hardware Security Test Interface failed and the device is not Modern Standby, Un-allowed DMA-capable bus/device(s) detected, TPM is not usable
Hyper-V - VM Monitor Mode Extensions Yes
Hyper-V - Second Level Address Translation Extensions Yes
Hyper-V - Virtualisation Enabled in Firmware Yes
Hyper-V - Data Execution Protection Yes

[Display]

Item Value
Name NVIDIA Quadro K2200
PNP Device ID PCI\VEN_10DE&DEV_13BA&SUBSYS_109710DE&REV_A2\4&3834D97&0&0008
Adapter Type Quadro K2200, NVIDIA compatible
Adapter Description NVIDIA Quadro K2200
Adapter RAM (1,048,576) bytes
Installed Drivers C:\WINDOWS\System32\DriverStore\FileRepository\nv_ref_pubwu.inf_amd64_b7e5dd1387001335\nvldumdx.dll,C:\WINDOWS\System32\DriverStore\FileRepository\nv_ref_pubwu.inf_amd64_b7e5dd1387001335\nvldumdx.dll,C:\WINDOWS\System32\DriverStore\FileRepository\nv_ref_pubwu.inf_amd64_b7e5dd1387001335\nvldumdx.dll,C:\WINDOWS\System32\DriverStore\FileRepository\nv_ref_pubwu.inf_amd64_b7e5dd1387001335\nvldumdx.dll
Driver Version 23.21.13.8816
INF File oem23.inf (Section102 section)
Colour Planes Not Available
Colour Table Entries 4294967296
Resolution 2560 x 1600 x 59 hertz
Bits/Pixel 32
Memory Address 0xF6000000-0xF70FFFFF
Memory Address 0xE0000000-0xFEAFFFFF
Memory Address 0xF0000000-0xF1FFFFFF
I/O Port 0x0000E000-0x0000EFFF
IRQ Channel IRQ 4294967291
Driver C:\WINDOWS\SYSTEM32\DRIVERSTORE\FILEREPOSITORY\NV_REF_PUBWU.INF_AMD64_B7E5DD1387001335\NVLDDMKM.SYS (23.21.13.8816, 16.15 MB (16,936,560 bytes), 09/11/2017 09:53)

send you the screenshots.

static images can just be copy/pasted in, or uploaded using the the button, or linked via the button

I still cannot replicate your results. Sorry.

Maybe try downloading the zipfile version from the website, and unzipping to a new directory (like a subfolder on your desktop). Close any open installed Notepad++, and run from that unzip directory; does it still behave badly? Because a brand-new unzip behaves as I would expect under those circumstances.

Here is the debug information:

Notepad++ v7.8.2 (64-bit)
Build time : Dec 4 2019 - 01:39:49
Path : C:\Program Files\Notepad++\notepad++.exe
Admin mode : OFF
Local Conf mode : OFF
OS Name : Windows 10 Home (64-bit)
OS Version : 1903
OS Build : 18362.535
Plugins : mimeTools.dll NppConverter.dll NppExport.dll

If you follow this link you should get screen shots and a description of how the problem.

http://www.hostellerssailingclub.org.uk/index.php/?option=com_content&view=article&id=148

Ignore the image and logo ‘Hostellers Sailing Club’ that appears at the top of the above linked webpage.

I hope this works, if not I will have to think of another way to send you the screenshots.

Thank you very much for the speedy help. I am surprised no one else has reported this, I dont think there is anything all that unusual about my computer.

Let me know if i can send anything else to help.

John

The first thing that comes to mind is a plugin interaction issue. If you give us your Debug Info … see the ? menu … it might help with diagnosing that. [This is also in Peter’s reply, but not directly]