Using REAPER 2.54pre2 or 2.99alpha7 (both unreleased but usually quite stable) I got crash once trying to load JS twice.
Step to reproduce:
Brand new project.
Insert new virtual instrument -> Select JS, cancel quickstart dialog
Insert new virtual instrument -> Select JS
Then crash.
I know it must seems stupid to use twice JS but hey, I'm into weird stuff sometimes...
I'm not angry, just wondering.
Dali