Yep. Try assigning your pocket knife to a letter, cut something up, and then look at inventory again. For me, the rags I create have the same letter as the knife. When I try to select one, I select both. I have to drop them both and pick them up again. I haven’t checked if this is only when my inventory is full, but it is annoying.
Adding thread to an empty sewing kit always changes its letter. Flashlights also tend to roam around: 1)assign a flashlight with 100 charges to f, 2) pick up another flashlight with 100 charges, use your flashlight and it will jump to another letter. This also happens if your flashlight becomes empty (all empty flashlights adopt the same letter). When you refill your flashlight it jumps to a different inventory letter.