I recommend using a g4560 or better CPU when using more than 7 GPUs. I would get a g4560 or g4600 and swap it with one of your celerons in your 1st or 3rd rig. If this solves the problem; I would upgrade all your rigs CPUs.
What is the concern running Celeron CPUs with 8+ GPUs?
I have 4 rigs with Celeron CPUs atm as follows:
1. MSI Z270-A PRO, G3950, 6x GPUs
2. MSI Z270-A PRO, G3950, 7x GPUs
3. Asus PRIME Z270-A, G3930, 8x GPUs (soon to be 9x GPUs)
4. Asus PRIME Z270-AR, G3930, 9x GPUs (when they show up)
The first 3 rigs are mining ZEC using EWBF and rig #3 with the 8x GPUs will run for weeks at a time with no issues.
Is the issue with Celeron's only with certain algos and miners?