a while ago i got a crate head for a cheap price (obvi explans issue but oh-well) and when i have it all hooked up only the right speaker jack works the other one almost doesnt work at all (has a sweet spot) this being said there must be a possible way to fix the issue; ive done plenty of google searches for fixes or alike problems so i decided to try my luck here. if anyone can provide help that fantastic.
Some jacks can be repaired by retensioning the tip tang. Depends on its construction and material. Some you can't get to the contact and some won't hold the tension. Usually it's easier to just replace the jack.

But - all is not lost. First try cleaning it, it may just be dirty. Get a can of electrical contact cleaner. Deoxit is a good one but NOT WD40 and similar. Spray some liberally on a plug and work it in and out of the socket 4 or 5 times. You are using the plug as an applicator.
Gilchrist custom
Yamaha SBG500
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100

Cathbard Amplification
My band
sounds like that will work, luckily ive got most those things laying around; if anything ive got got stuff laying around that could also fix the issue say those 2 are not the problem.

thanks man.