I don’t use ACF - but if you’re seeing differences in REGEX behaviour between ACF and Lucee…
Lucee has a “RegEx” setting in the Administrator.
So you can choose between “Legacy” (Perl 5 implementation of RegEx
And “Modern” - which is Java’s implementation of Regular Expressions.
Perhaps, alternating to the “other” option - to what you currently have set, might see your ACF RegEx - working identically in Lucee?