slow Download speed RBR50

I have 1Gig internet with suddenlink hooked to a ARRIS surfboard SB6190 and the RBK50 router satellite system everything updated to current firmware normally i always read around 800-900mbps on orbi app lately ive been reading around 450 suddenlink tech came out to check everything out hooked into modem and was getting 986mpbs hooked into back of RBR50 and couldnt get a stable reading he said it was jumping between 8mbps to 50 and was unstable coming out of router so i know my issue is the router any ideas? is my router toast or could this be a firmware issue just curious before i go buy a new system. any help would be appreciated

tech also reported upload speed at modem was 54 and upload at router was 52