if I resign from my current employer will this affect my universal credit?

I’m pretty new to the forum and I’m going to apologise in advance for the somewhat lengthy post.

Basically, in July 2021, I was on holiday and had a fall, causing 3 slipped discs. Fast forward 10 months and I have considerable amount of nerve pain to the point I can’t walk some days and other days I have to use a walking stick or lift heavy things anymore. From July to Feb I was receiving SSP from my employment because my job involves a lot of heavy lifting as well as ALOT of walking. They’re unable to offer me lighter duties and have recently gave me the ultimatum of reign or go through occupational health. When I chose the occupational health route, they’ve now told me that because I’m on a zero hours contract and that I’ve received the max amount of SSP from them that occupational health isn’t cost effective. Meanwhile, because I’m in a zero hours contract, I have been claiming Universal Credit to top of my wages since the start of the pandemic, but, due to my injury, last month I was told by universal credit that I have limited capability to work.

My question is this: if I resign from my current employer (because the likelihood of me going back to the job is looking slimmer as the days go on), will this affect my universal credit as I would have voluntarily left employment? 

Just for added context, I‘m 29 years old and currently taking Tramadol and Amitriptyline for the pain. 

Thank you in advance and again, sorry for the LONG post.