Just a tip:
I find my 350Hz optional CW filter in my FT817 invaluable but it stopped working while out this Sunday. I pulled the lid off today to thankfully find it had simply worked loose on it’s push on connectors. After re-seating the filter, I sandwiched a small piece of bubble wrap sandwiched between it and the case cover so hopefully it will stay put this time.
I suspect the same could happen to the FT857.
It would be worth five minutes work securing the filter if it saves it letting you down on a hilltop!