Funny story from my first cycle:
I had purchased quite a few 25Gx1.5" needles to inject my oils with.
25G is too small to be using for oils, and the 1.5" length makes it worse than if it was a shorter needle.
Drawing my oils took AGES even when the oils were heated.
There would be SERIOUS vacuum bubbles forming in the syringe barrel because the oil didn't want to enter.
I was also drawing 3CC shots so this was a serious chore.
Injecting was less than easy.
I would be pressing the plunger so hard that I was afraid my thumb might slip off of it (this force also is what makes the needle want to bend or rip sideways because your thumb isn't dead center on the plunger).
My whole hand would be trembling to the point where the needle would repeatedly start to pull out and I would have to push it back in all the way.
I recommend holding the needle with the index and middle finger under the two tabs rather than holding the barrel in your fist.
Try to center your thumb on the plunger.
The slower you inject, the less tendancy there is for the needle to try to tear sideways (but I don't think the needle tip is actually tearing your muscle when the needle 'tilts', I think either your muscle is 'bending', or the actual needle is bending elastically).