"Sticky" key repeat / keyboard lag in Windows Parallels

This problem has been reported before, but I've yet to find a satisfactory solution.
Basically, the issue is that pressing and holding a key seems to be accompanied with some lag in Parallels. On occasions (perhaps every 3rd to 4th time), releasing the key doesn't immediately stop the relevant function. As a result, Shift+arrow keys for instance will select more text than I want, which is hopeless when I'm editing large texts for work.

Disabling "Key repeat" in Mac system settings seems to eradicate the problem in Parallels. Though it has a habit of reactivating. This is not great when working in macOS however.
Also, plugging in a USB keyboard and connecting it directly to the VM fixes the problem in Windows, but this of course renders the keyboard useless in macOS.

I have tried everything I can think of, from completely uninstalling/reinstalling Parallels and the VM to changing various keyboard-related settings in macOS, Parallels and Windows.
Surely there must be some kind of permanent solution for this? After all, none of the other remedies are really acceptable for a paid product such as Parallels.
Any help would be massively appreciated