Manual drum brake issue

[72c20customcamper]

I redid all the brakes on my 68 consisting of new shoes, cylinders and had the drums resurfaced last fall . The brakes pulled slightly to the right so I adjusted the shoes to full lock and then backed off till there was drag on all four. I took it out today and was on my gravel driveway . It’s a long drive so I got it up to 20-25 mph and slammed the brakes. Both passenger brakes locked up and skidded on the gravel . Drivers side didn’t even disrupt the gravel . I drove around around applying the brakes and the left front/rear got warm so I know they are active. But not working properly I’m going to pull a drum and look at the shoes anything I should look for ?

It’s puzzling that one side isn’t working but the other side works great .