TU status ISR10 for TU activity (&1 &2) is active, which is inconsistent

What causes this issue?

TU status ISR10 for TU activity (TU_NUM: &V1&, TU_SR_ACT_NUM: &V2&) is
active although no TU assignment exists or no active door activity
exists.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.