Wireshark MATE configuration issues and advise

Hi, I have few questions relating to MATE

1. Sometimes when I open the wireshark traces, In GOG level some errors coming as undefined attribute with garbled characters. Some of them point to properly defined variables which I defined it as Extract. Why its causing issues. Is it possible to do some tracing/debugging on similar MATE configuration file issues

2. In PDUs, I extract variables from multiple protocol subtrees. Some PDUs will not have some subtrees, will this cause null AVPLs and cause issues. How can I use extract statement if the protocol/subtree is valid in that PDU. Can I use transform for that purpose ?

3. In GoG, can I match GoPs with multiple common values. If not how can we achieve to group these into a GoG

GoP X (a,b), GoP Y (a,c) -> a in GoP X has multiple values, a in GoP Y has multiple values

Sometimes when I re-open the same trace from wireshark with same MATE configuration, I see different behaviors (e.g some errors which were there do not appear again). Do I need to clear any cache inorder to wireshark to re-read the MATE configuration when it restarts ? I am storing the wireshark mate file in my desktop, not sure if it makes any difference