In short, no. Have never seen nor heard anything like that - a call to the helpline may help as they are able to process MHUpgrade.

Adding a datapoint to the thread, KUL>NRT, M fare, minimum RM760, maximum RM1190.
Note: this is the same range as a Q fare in October. Per my previous comments, I see no recent evidence for bid range changing over time, nor with RBD.

Someone had put in a maximum bid of RM1190 from the start and availability was looking thin. When I checked today 3 days out, an instant purchase price is available that matches the maximum bid (which is the maximum possible bid and the maximum actual bid).

When I try instant purchase I get an odd error message and when I check ExpertFlyer there is zero availability in Business so I presume the error relates to that rather than 'restricted airline rules'.

It's hard to know if the instant purchase price is affected by the availability of tickets or not....from my experience it is certainly affected by the bidding. If the instant purchase price really is pinned to the maximum bid, the fella that bid the maximum really is screwing over everyone and himself. If there was no bids, the instant purchase would be less. If people use instant purchase, they will take availability away from the bidder (assuming limited availability like a Japan route).