Making a standalone thread for this issue.
Read more from here and here, if needed.
For the Power BI PowerApp custom visual, If the app takes longer to load it will ignore the function set on a timer end.
(note that it will still execute the function on timer end but will ignore the lookup, or possibly the lookup will not be given the data in time)
I don't know whether this is an issue with data be passed through with powerbiintegration.
Or, an issue with the app itself.
If anyone knows how to fix this issue, that would be hugely helpful at this point.