It's rarely a modem problem. You have a coax problem. Ensure all connections are tight, any exposed coax is not damaged or rodent-chewed, etc. The downstream power levels are all over the place and you should probably have 4 upstream channels.
Where is the modem from the point the coax enters your house?
I have 2 boxes and a amp installed but how its all connected i don't know. I do know the connections are tight from where it comes through the floor to the splitter to the modem
You definitely need a service visit to get a tech out to inspect everything. If you're in a single family residence, ideally the main from the street or pole would have a 2-way splitter with one leg to the modem and the other to your tvs. If you're in a condo/apartment, the main is likely split dozens of times with multiple amps and the wiring could be a huge mess.
I agree that you DEFINITELY have a problem with wide variation in signal levels coming in from the cable system. As for the in-home wiring, your install should be using a 3-Way splitter coming in from the street, with the two set-top boxes connected to the -7 dB ports and the cable internet modem wired to the -3.5 dB port. No amplifiers, no extra unused ports.