Xfer case issues

[arctictraveller]

I have a Borg Warner 1356 manual transfer case. Back in November, it was popping out of 4 low, so on the way to Baja I stopped in at Agile and had them remove the unit for me. I then tore it apart for inspection and found the "C" clip from the end of the shift shaft laying in the bottom by the drain plug. Close inspection of all the parts only showed slight wear on the shift hub which I replaced in an abundence of caution. All other parts seemed to be in excellent condition, so the clip was replaced and I put it all back together. After that, shifting was positive and crisp, it went into 4 low easily and it stayed there. Fast forward to last week, and suddenly it went back to it's old, bad habit of sloppy engagement and failure to stay in gear. As soon as the weather warms up a bit, I'll pull it out again, and I fully expect to find the clip missing again, but the problem is, I don't understand why it's coming off. I'll inspect the shift shaft C clip groove closely along with the clip, but they looked fine before. I suspect something is forcing the shaft to move outboard, placing a high sideways force on the clip, popping it out of the groove. Most likely I'll order another shaft and clip, but if anyone has any idea what might be going on, I'd love to hear it as I have enough projects already and don't want to pull the xfer case a third time................ Thanks.