I don't know the Flextight software so I can't offer any help on that aspect of it, but I do a lot of colour negative scanning, mainly using a Nikon Super Coolscan 5000ED and sometimes (mainly for testing purposes) a Plustek 7600iAi or an Epson V750 Pro, all with SilverFast Ai Studio and I don't have this problem - the images open in Photoshop looking very close to how they appear in the SilverFast scan preview. I mention this just to make the point that regardless of the fact one is scanning negatives, this does not necessarily have a bearing on the problem you face. I assume you've checked with Hasselblad whether they've changed the negative profiles (which you may have "upgraded" to) some time before you starting seeing this problem.
The most I can do is recommend on how you go about the diagnostics. The place to start would be with an assessment of what changed in respect of colour management in the scanning software, Photoshop software and your computer operating system's colour management modules between the time you last had good results and the time you started to get unsatisfactory results with the same process .