My MT-7-235 has a flickering oil pressure gauge a lot of the time. It flickers indicating normal pressure and occasionally steady. Yesterday after landing from 30 minute flight the needle was steady taxiing to tie down. About 20 hours to next 100. Any suggestions

Check the wire crimps on the ring terminals going to the sending unit . Vibration just beats them apart. If this is the problem crimp on new terminals and improve the strain relief by adding an inch or so of triple reducing shrink rap ( remember to put it on the wire BEFORE crimping the new terminal) even better if it's the kind that has hot melt glue liner.

you could "T" in a test gauge for a ground run to verify if your gauge is faulty or if you actually have an oil pressure fluctuation.

When I bought the M7 from Jeremy, he advised me that as the oil gets warmed up it may start to flicker. His solution is to pull the sender and peen the opening closed a bit.

It worked

I assumed the sending unit must be in the firing line of the oil pump.

In the Texas summers, it will still start to flicker on a really hot day. I guess the oil gets thinned a little more.

I am running the AeroShell Oil W 15W-50.

I had all kinds of strange readings being displayed on my oil temp and pressure gauges in my RV4. Turned out to be nothing more than loose connections at the senders and failing connections at the crimps. Redid those guilty connectors and she has been rock solid since. Probably (and hopefully) it is something simple.

" I assumed the sending unit must be in the firing line of the oil pump."

It is not actually a sending unit, It is the 45 degree pipe/flare fitting at top rear of engine that the gauge oil line attaches too.
Maule brazes a tiny washer on the end and drills a tiny hole in the middle.
I don't remember the drill size off hand, but one can pein the hole for more restriction and thus less pronounced pulsing of the oil.

Thanks everyone for your help. I will try to sort it out with the information supplied.

Try blowing out the tiny oil line with compressed air that runs from engine to gauge. It needs that air cushion. And also check to be sure the fitting actually has the restriction in there.