Its a buggy tame. We're lucky enough to have 2 mosas. Have your higher health mosa get grabbed using a regular saddle, platforms seem to bug him out. Have a partner feed the pearls. If it ever grabs your tame and you read it doesn't want to be tamed kill it. You can't fix the bug and you'll lose the held tame if you wait. You can always get more pearls. Your tames are irreplaceable.

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