extbase does not recognize t3lib_ classes in models for backwards compatibility
When an extbase extension should be compatible in 4.5 and 6.2 branches, a model property with a prefix other than Tx_ and no namespacing causes fatals.
I had this problem with a protected static property that held a caching framework frontend.
To solve this, additional cases should be included in the TypeHandlingUtility.
The case t3lib_ is solved in the attached patch.