It's been months since I've been able to get Tranexamic Acid (for my debilitatingly heavy periods) at Boots - it should be behind the counter next to the Feminax, but it's constantly out of stock. I basically just have to work from home for a couple of days each month now, as my bleeding gets so heavy that I flood a heavy duty pad in 15 minutes or less. I just sit on a towel for the whole day and deal with the carnage.
Other things that seem to be out of stock regularly - LactoFree milk (for husband), Oatly Barista edition oat milk for me, V8 Juice, brown mushrooms, broccoli, and Jackson's bread. On top of that there will regularly be fresh food shelves that are either empty or barely stocked.
This is in Leeds, at Waitrose, Aldi, and Morrison's for the most part. Is it similar where you are?