eS98 hangs with both Micro SD cards inserted

[iplat]

Hi,

We just recently installed brand new set of eS98 with CPT-120 and Quantum radar on the boat.
Our customer is complaining about subject issue.
MFD is working fine with only chart's Micro SD inserted to any slot. And it hangs forever after inserting Micro SD to second slot, until being restarted (long press on power button). It's happening after some undefined time, 1-60 minutes from insertion of the card.
Yes, of course, he bought best of the best brand new class 10 Micro SD card from SanDisk, it's formatted as FAT32. Then he took a couple of others brands/class/price/quality. Issue is the same with all of them.
We have opened warranty case and received new display. I brought it to the customer. Checked new display with same dual cards inserted, but using mine card, which I use for MFDs upgrading. And found received display hanged as previous one.
For some reason, display came with previous software version, so I decided to reboot it with both inserted cards. And whole upgrade process passed fine, without hanging or error messages. So, look like hardware of the MFD is fine.
Do you have any advice how to help the customer?

Best regards,
Ivan.