Voice memos taking up too much space in iPhone SE version 15.7.9

I have an iPhone SE

latest version software 15.7.9

though I have deleted voice memos it still reports 12,95Gb of data used by Voice Memos (Dictafoon). This is not correct and obviously a bug.

this has been reported before by many users and the proposed solution is installing software version 16.x.x which is not possible on the iPhone SE

will this be fixed in a 15.7.x version?

is there any other solution than completely returning to factory settings and losing all data?

my iPhone will be useless if this is not fixed