Not sure if it is the same circumstances, but I had issues with chemclean,
I have tried to link the thread below:
https://www.thehomebrewforum.co.uk/threads/chemclean-residue.101585/
If it doesn’t work just search chemclean residue.
Long story short I found that neat Chemsan / starsan removed it really easy. I have really hard tap water and even when only letting it soak for 20 minutes I got the deposit. I got fed up with it in the end and have now moved on to the brauland cleaner. Only used this to clean kegs so far but no issues as yet. Hope this helps.
