Speaking for myself, luckily I have a test environment where I tried everything before upgrading. So the production site is ok as I didn’t upgrade.
I am migrating from WP 4.1.1 so it may also be an issue due to how WP handles upgrades, or to a plugin which makes use of ACF or anything else.
I don’t know how to get term_id’s unluckily but I may try to find them with some advice.
The affected terms exist in more than one category.
One more note: Not all the field values are deleted, it seems that nearly 10% of them is still filled …
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