I sympathise with burying cables that you think are for life, only to need to replace them later.
We ran fibre cables in the ceiling when constructing our house. I requested the electrician to shield the cables with some tubing, but he probably thought I was being extreme. We have 9 cables, 2 of them don't work, likely from being bent by mistake or something.
The wiring is intermixed with electrical and ethernet (for cameras) cables, making the process a bit tricky. At least for us we might only have to cut the ceiling boards in a few places to help guide the replacement cables.
9/10 times the problem is at the terminator - they can get yanked out of position if they are pulled rather than the sleeve. Snip off the pulled end of the suspect line with Kevlar shears and shine an OFF down the other end - and you’ll probably see laser. It’s then a surprisingly simple job to re-terminate with mechanical connectors.