First of all, I have to explain a bit.
While my main laptop is doing intensive work (update ?) decided to update an old project using a MacBook Pro M1.
Of course, witj Xojo 2021r1.1.
So, the work goes and goes, and finally, I move the project to my main laptop (MacBook Pro i5, El Capitan, Xojo 2015r1).
Then, when running n the IDE or as Stand Alone, when I click in a Canvas button, I get its image nverted for around 4 seconds and it tooks another second to display the new window.
This behavior exists nly for this window, not for the other windws (I do not changed the code on the other windows)
The “original” project works fine.
On M1, I cannot talk about a slowdown because I get a dialog asking permission to use data on disk before the new window is displayed.
It may not be a good idea to move a project from version to version.
And, of course, when I will have some minutes, I will rollback the new code to the previous version and discard this project once all goes well.