I resonate with this and feel for you.

This could be cognitive as someone suggested. Maybe the start of Alzheimer's as dementia impacts memory. Although 2 sides of the same coin, A and D seem to go hand I hand as A can develop into D.

My mum is similar. Although not tested (A and D are strong on my family) her cognitive abilities have declined. She's 67 and will fixate on seemingly minor details such as your mother and the timings etc.

Hope you're ok