Are you doing situps/back extensions?
I've seen versions of this post before but looking for thoughts given my specific situation. I'm 42. Spent ages 38-40 really trying to get as strong possible and added a lot of weight and strength while working with a SS coach, but had to eliminate some of the weight for health reasons (was causing really weird stuff). I still lift though have backed way off of former PRs, which is why I'm stumped on this. Everything is progressing as it should except my deadlifts, which used to be my specialty. I had a pretty significant disk injury (have never gotten imaging for fear that they would want to cut me up) when I was towards the end of the heavy lifting phase of life, and now every time the deads get hard at all, I get a little pop halfway up a rep and I'm down and out for a couple of weeks. Have tried everything from extended rest and rebuild via NLP to (gasp) sumo. Results have been about the same when I get to working sets around 375 (happened today during a warmup set at 315, which is normally real easy). Squat, bench and press have all progressed as expected, but dead is stuck.
I think my form is good, I've had form checks, and I'm sure it breaks down under max effort but was moving 570 lbs on the dead without injury a few years ago. Now I'd struggle to pull 405 more than once (on a healthy day). At some point it's hard to keep deadlifting given the cycle and how much it costs me on the other lifts and life in general to have 2 out of every 20 weeks be hindered with a back tweak.
Are you doing situps/back extensions?
Could be the situps. This will heal in a few days.