With stable 4126, I could have several sublime text windows opened each connected to a website through SFTP and have all simultaneously doing a find-in-files search.
And it all worked perfectly.
Now with the most recent stable sublime text builds 4142 and 4143 only 3 sublime text windows actually start downloading the files for the find-in-files process and the remaining st windows will only start the download of the files as long as the first 3 windows complete all the find-in-files process one by one.
I have managed to trace this change in behaviour back to the build 4130, with suspecting changelog entry " * Find-in-files now works in parallel".