There may have been an update to the portal @Xavier L , we'll have to track that down. In the meantime, do all you tags still show up when using the following command?
az acr repository show-tags -n MyRegistry --repository MyRepository --detail
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EDIT 2022 Aug 18 Thanks for confirming the CLI command returns all expected tags. This seems to me like a UI/UX update on the portal. I'll get confirmation and pass your feedback along.
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EDIT 2022 Aug 19 This is a reported issue and will be fixed in a future update.