Modifier with disabled `i` flag doesn't match correctly

[hugo9655]

Bug Description

With the following regex, the contained group sometimes fails to match case-sensitive:

If you tinker with it for long enough, or type out the match differently, sometimes it will work:

This behaviour is wildly inconsistent, but can be replicated with minimal attempts.

Reproduction steps

Find the exact pattern here: https://regex101.com/r/3iZcI2/1

See that its incorrectly matching from the start. Type out the match in different ways, maybe from start to finish, or deleting and re-typing an individual letter, and you should see the inconsistent matching happen as ive described.

Expected Outcome

Consistently match the target string case-sensitive.

Browser

Tested on latest Firefox and Brave (chromium)

OS

Windows 10

Notes:

Ignore the other redundant parts of the regex, those are needed for my specific use-case, including the global case-insensitive flag. Im just reporting the bug thats being caused by the Modifier capture group.

[hugo9655]

update: looks like its not an issue with regex101: nodejs/node#60030

i will leave this open for anyone else having issues