If the 150x5 was without Flyes first then that’s at least part of the problem. You could also just have had a bad day. Also if you didn’t keep working in the higher intensity low rep range you could have lost some ground in that weight range since your muscles will tend to adapt to the rep range you spend the most time working in. Another possibility if it persists is that you could be overtraining and/or not recovering enough between workouts.
I’ve been in your situation in previous cycles and there are two things I’ve done. If I feel I’m overtraining then I just drop the DB Presses, otherwise I just switch over to BB presses which should allow you to handle more weight.
I’ve had the same thing happen to me. The pain runs so deep it feel like my bone marrow hurts. I found that cutting the frequency and or volume some helped out a lot. For example in my first two cycles I did simple push/pull/leg full body workouts every day until I couldn’t progress. Then keeping the same exercises I rearranged them so each body part was getting worked every other day until I stopped progressing and finally rearranged the exercises again so that I was working out each body part once every third day. Another way I did it was to drop some isolation exercise as things got very heavy.
Try experimenting around and listen to what your body is telling you. You’re already using Myo-reps/clustering which requires you to pay attention to your body so you can push close to the limit without burning out. Try doing the same thing by experimenting with the volume and frequency of your exercises.