Questions about a used Rws 34

I bought a used Diana .22 34 and was generously given a new .177 34 from a forum member here. I haven’t had any problems with the .177 but the .22 is disappointing.

I’ve only shot maybe 100 pellets thru my new to me 90’s era 34 and I’m still trying to decide if it’s me or the rifle that is inaccurate. It’s VERY hold sensitive, just the slightest difference in hold causes at least an inch difference in POI. Is this normal for a 34? I’ve read reviews of some other springers that say they aren’t hold sensitive at all so I’m wondering if I just got unlucky? I can get much better groups with my 34p .177 using the same hold(s) and it doesn’t seem nearly as sensitive.

Another question, I’ve been shooting jsb pellets from a sampler pack and sighted in using the 14 gr pellets at 15 yards. The heaviest 20 gr jumbo pellets I expected to impact lower but they were grouping about 6 inches HIGHER than all the others. How does this make sense? 
 
I did check the screws. One thing I also forgot to add is that I’m using the jsb sampler pack and all but the jumbos fit very loosely in the barrel, the Stratton’s would sometimes fall out while I was closing the barrel. If they’re that loose at the breech I’m guessing maybe they basically bounced down the barrel and that’s why I’m not getting good groups?