Just picked this up from the dealer and took it to the range for the first time. About 90% of the time after chambering a round or after each shot, the hammer goes back to half cock. I'm guessing this won't be an easy fix, maybe a sear issue?

I've always had good luck with surplus guns, I guess i was due to get a lemon evetually.

Im having the same problem, and can't find any info, bump.

No experience but a google search showed someone with a similar problem and the sear was peened.

You can start checking the sear and hammer to look for damage

I know this a old thread but since no one answered I will Relay my experience.
I too bought a Star BM In 2018 With exact symptoms described.
I suspect there was a large batch of them that came in with all the same problems.
Upon disassembly it was clear that at sometime in the past someone had done a “trigger job” By filing the sear notch on the hammer down till There was almost no engagement with the sear.
I took a small flat jewelers file and filed below the sear notch on the hammer until I the seer had full engagement with the sear notch Which fix the problem.
Be careful not to go too fast as the steel on these hammers is not that hard
Hope that helps

ETA: @TxAggieA-Batt @coltshorty14

The sear spring is similar to the 1911 design.
adding a bit more tension by bending it forward a hair may fix the problem.
On a gun that old , if it was me, I would try to replace all the springs.
Recoils springs are often tired on used guns.
You can find replacements at gun parts corporation