bad pip cuz bad gear, or if not that, needle too big, or not kept steady during injection, or you inject the oil too fast,or you are unlucky and hit/pass through a blood vessel or a nerve.
Cuz I bet you are not injecting exactly in the same exact spot..so even if you go 3-4 cm in any other direction with next injection from the original inj spot, there shud not be any PIP. It's like very simple if you think about it abit.
If too complicated, then just go inject in Quads ( like 1 palm min distance above the knee, to the outer side), then Glutes, by rotation.

in the long run over pinning high volume in the same site over and over again will soon take its toll ,after years like this that muscle will super damaged its fibres will be weakened,also become leathery and lumpy and also loses the ability to absorb any depots etc..
try to spot inject all the diff muscle groups,always work on the inj site both prior and post injection this will massively help over the years

On my current and previous cycle I've been pinning 2ml per shot in the glutes - last cycle I was pinning twice per week, so each glute got pinned once a week, this time I've changed the injection frequency slightly and am not sticking to a weekly schedule but pinning every four days (so I get around to pinning the same glute every eight days). I'm also pretty careful to rotate the spot on the glute that I inject in. I use a 3ml syringe with a 23g or 25g one inch needle, and warm the vials/amps gently in a clean heated towel prior to injection. For me that works perfectly, no pip, no site swelling, redness or soreness etc.

I used to work as an EMT many years ago and it's interesting - in bodybuilding circles it's usually recommended that, to reduce injection site issues and risk of infection, as well as to establish more stable levels, you lower the injection volume but increase the injection frequency. In most medical settings though they look at it the other way, that every time you pierce the skin no matter the volume of the injection, you are creating a risk for infection and potentially damaging an injection site by repeated injections, so for IM jabs they tend to recommend fewer larger shots if possible for the drug involved, if many jabs are to be given over time. The standard recommendation for volume in the glutes is 3ml or less - with thighs I think was 2ml, and 1ml or less for other sites. Those volumes are generally considered safe for fairly regular pinning for an adult of average muscle mass or greater so long as injection technique is correct and everything is sterile etc.

My gluts get the shit pinned out of it. I bet they look like Swiss cheese ;)

Oh dear!
You likely leaked out and missed the muscle entirely
But since you didnt give us the pin size and compounds and amounts, I have no clue where to start

Also, needle length and gage?
My delts and quads I use a 28ga 1/2”. I don’t have a lot of fat in those areas. Glutes I use a 25ga 1”. More skin and fat.

Im doing TRT doses of test c.

3x wk is still alot of pinning. Ur going to have to learn how to pin other muscle sites to give ur ass a break. Need to add delts and quads for a start, but honestly if ur going to be doing advanced cycles requiring frequent pinning, u need to learn ur muscles pin points. I don't hit the same pin point more than once a week..

As far as more advice and tips, we would need to know more about ur cycle and how experienced u are with ur pin procedure.

How many cc’s you injecting at one time
I like left delt, right delt, left pec , right pec
Right glute , left trap , right trap

Are you going straight into the muscle?
Try going at a slight angle in the direction of the muscle. Inject slow.
I inject 2x a week. I do both in the same muscle but different area of the muscle and I rotate. Ex: Monday, towards rear of right delt, Thursday, towards the front of the right delt. Following week I’ll do the left, then onto the butt cheeks, quads…. Basically hitting each of the six main sites once every 6 weeks.
Plenty of YouTube videos you can watch.

1x/week. the longer between injections the better, especially if over 1ml. Start breaking in other sites. Delts/glutes/quads.