This has happened multiple times and I never received a reply from staff, yes I know how the star system works (losing stars, etc.) but this is 100% an issue; screen shots for proof below.

Upgraded from 8 to 9 stars, as you can see the 9 stars are there.
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Usually when a star succeeds, you will get a 'power up' message. I did not get this message however, so I closed my heroes UI, opened it again, and I was down at 7 stars:
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I did not click more than once and lose stars I always wait at least 3 seconds before attempting again.