The number of Gimp versions is not an obstacle in this case.
Some work awaits You:
If they differ in size, it probably means that they act differently (and affect each other by identically registering in the script-fu-register).
Unfortunately, it is not known which script works well and which does not.
You need to get rid of all duplicates one by one (eg move all listed first in the "Duplicate Items List" to another place outside of Preferences).
If it works fine - after the problem - if not - you have to do the opposite (move the second and restore the first).
When you're ready, let me know.
Small Request: for BRL: please move to another location: bevel logos-LOGOS & ALPHA_bevel-preflect-logo.scm and bevel-reflect-logo.scm (1.6?) and try again in 1.7.
Also, look for the number of gimpfu.py and script-fu.exe files you have.