Error during coregistration

Dear colleagues
I have tried my best to coregister my images in SNAP ver 8 but I get this error
Error[Nodeid:back-geocoding] org.esa.snap.engine_utilities.gpf.stackutils.isslaveband(lorg/esa/snap/core/datamodel/band;lorg/esa/snap/core/datamodel/product;)z

What could be the issue here? Thanks for the help

Please provide enough detail so others can reproduce the problem (see the FAQ). In particular, you should mention your OS, SNAP update status, and the input data you are using. There may be useful information in the messages.log file (from the Log Directory, whose location is shown on Help Menu).

Also, please update to the current version 9.0

Thanks this solved the problem and I have successful results