I have these Lexeme with a Sense and a Form. 2 editors (A and B)
B edits the Lexeme by removing the form.
few seconds after, A tries to edit the Lexeme by removing the Sense and gets an Error: sense Id not found. A only succeed after reloading the page
I repeated and got a different output, it works just fine: https://wikidata.beta.wmflabs.org/w/index.php?title=Lexeme:L52&action=history
(Did you make sure to refresh the page after you added senses/forms?)