I agree with you that everything you’ve tried seems to point at the newer than 1.3.0 firmware being the culprit. I was only pointing out the dongle option because I notice that it’s only option you haven’t tried in case you may have one that came with your ConnectClip that you can just pop it in to try. If not, then it’s probably not worth trying, although it can be bought for around $35 from eBay if you’re desperate enough that you’re willing to try anything at this point, at least to rule yet another thing out.
Using the dongle doesn’t necessarily imply that there’s a reliability with your laptop BT, because you’ve already proven that your laptop works just fine with the ConnectClip and the OPN and OPN S. However, there might have been something buggy about the firmware in the OPN and OPN S before that required the dongle to resolve when connected to the ConnectClip as the intermediary device to the PC, but subsequent OPN and OPN S firmwares resolved the issue and made the dongle no long necessary. Perhaps the post 1.3.0 firmware broke something similar to how the OPN/S firmware was broken which the dongle fixed.
OK, ideally Oticon should have fixed it in the 1.4.2 firmware of the More, but apparently they didn’t fix it like they thought they did, specific to your situation. So it depends on how desperate you are now to blow $35 on a dongle to either rule it out or maybe hope that you get lucky, vs holding your breath for god-knows-how-long of yet another firmware for the More that may not be until another 6 month in the making. If you need this for work and you can expense the $35 dongle as a work-related item then maybe it’s a worthwhile thing to try (if anything just to rule it out).