Most likely two possibilities, the locking pin is bent, or the mount is twisted. The rubber bushings have enough flex that you can actually twist the mount if overtightened. You can troubleshoot the mount with the trolling motor removed. Start by loosening the mounts until just snug and ensure that it latches in both positions, then slowly tighten each nut. If that doesnt fix it, check for galling on the slot that the pin slides into. I had a gator mount years ago that started to deform in the slot and was difficult to release from stowed position. Hitting it with a file fixed the latching issues, then I discovered that the mount was slightly twisted which caused the issue in the first place.
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