from what i understand is that if your membrane sees temps above 45c its pretty much nuked. I am not 100% sure why but am going to try to find out. maybe someone else here knows why.
Have u tried it again with cold water?? Try it and read the tds......
Just out of curiosity......do you still have the rodi water you made with hot water?? If so check the tds on it too.....
I ran hot water thru mine by mistake once and it didn't do anything to it. It was on hot for about 10 min before I noticed it. Ran cold thru after it sat for about an hour and it came back down to 10 TDS going into the DI chamber.
That was about 6 months ago and it is still sitting at 3 TDS before the DI.