Sorry I can’t be of more help right now.
Another observation:
This is your transaction: https://chain.so/tx/LTCTEST/2e02c3177ff2f7c5230950139d45d04c51672625dd9772affa3b4cc452d4f077 It sends 2 LTCT to address 2N84AKp4kqNg7BPbpbbTMY6BztREabRewyS.
Your deposit address QUBozNWtD9PDSaC9RC6b77nmvFCL56foY1 is a P2SH address (see here). These were introduced recently.
The deposit will only work if the address the plugin reports is the same as the one in the IPN message. From what you say it seems to be the case. I will check to see if this somehow causes problems.
It seems that you have done everything correctly. It is unlikely that this is due to some plugin conflict. You can easily check by deactivating other plugins.
I will let you know if I find anything of use.