You can manually pull the arm32 image and specify it in your docker run command.
So:
docker pull storagelabs/storagenode:5f2777af9-v1.50.4-go1.17.5-arm32v6
The stop and remove your container and modify your docker run command to use the specified image:
docker run.....
..........
--name storagenode storjlabs/storagenode:5f2777af9-v1.50.4-go1.17.5-arm32v6
Once the issue is fixed, you can change your docker run command back to latest. I don’t think watchtower will update your node until you set it back to the latest tag.