I have adjusted up / down under pressure for many years with no problems.
True my Maverick i got on release back then i have changed regulators on, but not CUZ they was broken / not working, and then there was that one time with the brain freeze where i thought my front regulator was a bleed screw, so that cost me two new 1x2 mm O-rings.
I also adjust my Epic two up / down, between 30 BAR to about 110 BAR depending on what i want to shoot, that did not hurt the Huma regulator i had in there for the better part of a year, and the new Epic one regulator i run seem OK with it too.
The epic Two is a single regulator gun, with 300 BAR in front of it.
EDIT:
I of course do NOT go from 110 BAR to 30 in one go, i do about 5-6 adjust - shoot to bleed and look ( at gauge ) before i am there.
And as 30 BAR is at the very bottom of what the regulator can do, i some times go to far and the regulator turn into a valve that is OFF, so when gauge is under 30 i open regulator to when i can hear it regulate and see pressure go up.
PS: I need very low pressure for lighter stuff pellets ASO, otherwise they fly too fast out of the 700 mm barrel.
And even if i am a slug whore, well dropping the pressure a lot like 2/3 and then load up some pellets, for some in close wholesome fun, well i like that too and will gladly shoot a tin or two like that on a nice summer day at the range.
Everything within 50 M and small is in mortal danger of getting flattened brutally ( flies ) or cut to pieces ( branches - flowers - blades of grass )