Juan, believe me - I am NOT laughing. I do not envy you the task of hunting this bug down. And my offer of my time and PC, via Teamviewer, still stands. I will send you an off-group email with my mobile number, you can send me an SMS Text message and I will do my best to 'appear' for you.
And another tip for those troubled with this 'bug'. With one 'instance' of PixInsight running, start a SECOND instance of PI at the same time. Then close both instances down.
What you will now have will be the PixInsight.ini configuration file (as described earlier by Juan), but it will have two (identical, at this stage) 'sections' within it. Now, the way I work things is that I edite the SECOND half of the config file, and make my [0.0, 65535] change to the SECOND INSTANCE ONLY.
This allows me to load my Meade Envisage 32-bit Float images into the SECOND instance, and to then convert them (with an ImageContainer and the SampleFormatConversion process) to 16-bit Unsigned Integer format - for use whilst I calibrate the data.
The actual 'calibration' steps are still carried out in the 'first instance' of PI - because all the data is, by then, in 16-bit UI format, which is perfectly 'OK' for PI, as it meets all 'common sense' FITS standards.
Once I have converted my data into 16-bit UI, I can close PI(2) down until the next session of data needs to be converted (a process which takes, in the grand scheme of things, almost 'no time at all')
Hope this helps.
Cheers,