I ran into a problem with prep saving. It would say "There was a problem with the flow file. The data may be corrupted" with no further information. Error message was not able to be copied and I couldn't find anything on the issue. The font is also at like 7pt for some reason.
I ended up losing all the changes from the previous save and started saving after every step to see if i could find the issue.
The issue occurs when I insert two "clean" changes into the same step. Any time a second clean change is added, the file won't save. if they are in separate steps or if the calculation for the clean step is copied into calculation, then the file will save fine.
I couldn't find anything on this, so I don't think it is that common. One thing that makes my situation unique is that I started the file in 2018.3.1 and went straight to 2018.3.3.

Hi Josh
Looks like this post was made over a month ago but for some reason the format is 'Document' rather than 'Question', which likely explains why you didn't get a response.
Did you end up contacting Tableau tech support about this?
Note that the latest version of Prep is 2019.1.1 released 10th January Tableau Prep | Tableau Software
Kind Regards,
Ciara