I've not had a need to disassemble my Road Morph, other than replacing the end bits with the Topeak kit TRK-RP01 that is, and that's a doddle - simple unscrew the end bit and swap in the replacement parts.
Tbh, It's not a pump I use a great deal now. Too big to carry on the bike and not really up to it as a pukka floor pump either (the gauge is, um, 'indicative' to be kind) It fell out of favour for me after I bought a JoeBlow many years back.
However, assuming it's not the end bits/seal (and it doesn't sound like it), I have read of internal o-rings that do degrade and require replacing and/or re-greasing with silicone grease. Some people do that as a matter of course every year. As to HOW one accesses them, AI tells me....
To access the internal O-rings on a Topeak Road Morph G, unscrew the black plastic cap located at the top of the pump barrel, just above the hose attachment clip. This cap is thin and may require needle-nose pliers or fingers to grip and twist counterclockwise. Once removed, the plunger assembly can be pulled out, exposing the main O-ring on the shaft. Some users report that the handle base can also be used to help unscrew the cap if pliers aren't available.
Be cautious not to lose small internal parts during disassembly. After cleaning or replacing the O-ring, reassemble in reverse and apply heavy grease to ensure smooth operation. If the cap is stuck, Topeak’s customer service often provides support and replacement parts upon request.
Some/a lot of the above is from a thread on Bike Forums, you'll need to subscribe to view it....
https://www.bikeforums.net/touring/321857-topeak-road-morph-maintenance.html
