T. G. J. Rukmal wrote:

ESpeak synth has been doing a fine job of reading text typed in this language using unicode until  NVDA version 2020.3. Thereafter, even in V 2020.4, we,
the Sri Lankan users of NVDA  came across a lag while typing in Sinhalese unicode in MS word and even in google docs while using both Chrome and Firefox

Go to https://github.com/nvaccess/nvda/issues, and create a new bug issue.

The template you fill in there will ask for all the basic information that is needed.
You have described the issue pretty well here, and if you provide this information it should be a good start.

Report things like a common current Windows version, whether you've run without add-ons and get the same results, and whether you're able to downgrade to (or use a portable copy of) NVDA 2020.2 or earlier and get the corrected results again.

You can also search there for other issues similar to this, although personally I don't remember hearing of one.

Luke