I have a 98 Suburban with the 350. The canister on the AC lines are mufflers - that's according to my neighbor who is the lead tech at the GM dealer.

The front evap discharges into the accumulator because of the orifice tube. I think this site does a good job explaining the difference between the receiver/drier and the accumulator.
https://macsworldwide.wordpress.com/2010/07/13/three-important-functions-of-the-receiverdrier-in-your-cars-ac-system/

It's hard to make a guess about what the issue(s) could be. I would probably start with putting on a set of gauges before the problem started to establish a base-line, drive it around until the front AC quits, then put the gauges back on.

Are you 100% sure there is no issue with the blend door?

As sure as there's no change in air volume through the dash vents when cooling goes away, and the front heater core is disconnected from the cooling system.

Sixto
MB-less