2023 I think I know what started this very loud internally heard crack. 18 months ago bought an adjustable bed and keep it in raised position during day and down at night: lately I leave it half-raised ... so my head is raised with pillow for my digestive tract and eye pressure re glaucoma....it is fine when laying or lying on my back but I wake up sleeping on my side and therefore my neck/top of spine is crooked... I doubt if will be able to fix and not sure where to go as am 79 ... agree does not hurt but many other things do and this is a bit disturbing and I feel I caused it myself!!! I already have tinnitus etc. etc. so more noise in my head!! I would suggest if you have a bed which can be raised, to keep it flat at night...... J.