Bit of advice please. I'm trying to remove and clean the flush valve washer as I suspect it's either worn or needs a clean. (Toilet is not filling and emptying water straight out into the bowl). However, from reading a post on here it appears that I may have to give the unit a 90 degree turn to remove, but it's just not budging. Without wishing to break the unit, am I just being daft and missing something obvious? (Picture attached with the offending catch and there is a second one on the opposite side). Cheers.