With the functionality of LLD overrides and host prototypes, it is possible to assign templates and install macros.
In the case of communication failure during data collection, it's possible to have a job halfway done. A received host list comes in full, but the tags array is empty.
If the override rule is based on tags, this will unlink the template and erase existing history.
The odds of having this situation are very low (1h LLD frequency, host list OK, tags array not OK). Probably 1:10000. But when it happens, there is immediate data loss which is beyond repair.