I have had few tiles comes loose in the upstairs bathroom (6 year old.. no bounce on the floor so only thing I can think of is that it was not applied correctly).. I want to prepare the floor to reapply adhesive and wanted to check what's the best and easiest way to remove the old adhesive?
I have tried the scraper attachment on a multi tool but it failed.

Please advise.
I have tried the scraper attachment on a multi tool but it failed.

Please advise.