It turns out that I was mistaken. My code doesn't work fine with large arrays. These are my events (CurrentColumn is a local static number defined above):
With the wait statement in event 32 enabled, Construct just goes through the Array very fast, but the entire loop ends before everything is actually loaded. It doesn't seem to wait the 0,5 seconds per CurrentColumn. With the wait statement disabled, the Array eventually loads as intended and the browser prints log messages during the loop, but Chrome says that the page is not responding and the progress bar is not updated during the loop.
I am using this to load a very large csv file, exported from Tiled and containing 400 times 400 tiles, so the calculation of each row takes quite some time, up to 1.5 seconds. I have tried with different wait times, up to two seconds, but without success. I guess that I am doing some obvious mistake here, but can't figure out what it is.