This is really odd behaviour. I've tried to strip down the minimal text to cause the problem. File is attached in .ZIP, but contents are also below to try and explain the problem.
Version 14.52 64-bit running on Windows 10 1909
Open editor
Open the sample file (Test8.txt)
Double-click on the item in the 1st line "CAM_ADDR_BASE"
CTRL-C to copy
Double-click on the 4th line "CAM_BLOCK_EGR"
CTRL-V to paste. May have to repeat the double-click + CTRL-V several times for it to happen
Line gets transformed into CAM_ADDR_BASE set bit_list {"" "CAM_RTE_EXCEPT" "CAM_DPORT_EN" "CAM_DPORT_PR" "CAM_DPORT"}
This is just one example, but there are several similar cases during my editing where the line gets corrupted in various ways. The only thing in common is my double-click to select and then copy, then double-click to select and paste.
It seems a little crucial that you do not do anything else other than the steps above. For example if you CTRL-A to select all and then re-paste and try that again it seems to not cause the problem so easily.
Contents of text file: # CAM_ADDR_BASE (CAM_DATA_REG_4)
Also additional note: Using CTRL-Z to undo the error doesn't restore the previous state correctly either so it's basically close the file without saving and re-open if you want to recover.
Seriously, pasting after double-click works OK more often than not; sometimes this glitch occurs, though. I never managed to spot it with lorem ipsum, and also never on Windows 10 machine (maybe I didn't try hard enough), but on Windows 7 (probably irrelevant) and with the original sample from u00000000 (which may be relevant) I am able to reproduce it from time to time.
Alium tibi quaere fratrem; hic, quem tuum putas, meus est. Titus Flāvius Caesar Vespasiānus Augustus