This happened to me once durring normal gameplay and aftter testing this is how I got it to work again:
Take off all equipment. Put on a ring of woe a crown of woe and a ring of doom. Buy food from the Scorn food shop.
Buying with my normal equipment and buying without anything on did nothing.
I lost exp in my two highest skills. The skills are also the ones that I gained exp in last. Praying and 2 handed weapons.
This first happened in a magic shop (I foget what magic shop) and I had normal items on (nothing that lowers stats).
This is also my first bug report so let me know if I did things wrong or anything weird. Thanks.
Thanks for the report. I did manage to reproduce this bug on Invidious, but not on the latest development sources. This issue has already been fixed, and Invidious will receive the update soon.