Rather than bug(s), there are some proposals for extensions and I believe some patches are submitted.
The current code in 3.2.0 and before is very stable. It is just not feature complete in border cases. (back propagation and the likes)
Note you can not simply copy any regexpr from other languages, because you need to adjust some expressions to Pascal escapes.
Your fail string has nothing to do with TRegExpr. It is not even a fail string.