Intermittent internet performance w/RBR850

Folks. I recently upgraded to a RBR850 mesh kit with satellites. Firmware and everything is upto date. Lately the last two weeks, my internet goes between 20M to 300 up & down during the day. I updated the DNS and channels 2.4 Ghz to 6 & 5Ghz to 48. Works fine most of the time but still experiencing up/down internet performance. Could this be a ONT/FIOS issue? Please advise. Thanks