Had the same issue with Fork + BitBucket. I don't know what was the cause. But here are some insights:

• I added commit with 3 images 0.7MB each.

• I tried increasing the post buffer even though I've been working with much larger files before.

• I checked my repo size - far below the limit.

• Tried restarting the Fork app, entire system.

• Tried removing branch from the origin and pushing it again.

What actually solved my case:

• Created alternative branch before the problematic commit.

• Pushed it to the origin with no issues.

• Cherry picked the problematic commit.

• Pushed it to the origin with no issues.

What's more interesting I also went back to my original branch and tried pushing once more. It went successfully with no issues.. I suppose there was some caching issue somewhere.