I'm not going to exclude the possibility that they are having some rather typical reliability troubles with the new engine but the idea that it's fundamentally flawed seems a bit far-fetched to me. Considering the long lineage of MBT prototypes prior to the T-14 I don't see how they'd have ended up selecting an engine that simply will not work right.
The fact that the T-14 is somewhat heavier than prior Russian MBTs and the advanced electronics does mean that Russian logistics will have to adjust and that probably poses a major challenge given the wartime situation. I do believe the program has been de-emphasized and considering events that is probably a reasonable choice, but I do not believe it has been cancelled despite the claims that it has, claims which seem to occur multiple times a year now.
Even if trials were to find deficiencies requiring major redesign, I think it would be unlikely for Russia to cancel it and start with a new prototype simply because of the pride/propaganda/reputation factor that has become attached to the T-14 and the other AFVs in its family.