I suggest taking a look at your html sanitization settings make sure html isn't allowed in markdown settings.
Next step would be to move the other 2 topics from that category and check if you still see broken markup.
After importing my db from vbulletin the mongoDB ended up with a null user with id 0
on users csv i got this
that makes some plugins crash
how can i remove that user ? i´m not a big expert on mongo shell comands
Please look here.
thank you, i understand the procedure for null topic but not sure for null users