Hi there
Just to add to this, I am experiencing exactly the same problems as @mlooijengoed.
Bulk Smush.it resulted in “Did not Smush.it due to previous errors” after one of the images exceeded the max size.
When i try to re-smush (after fixing size) the bulk feature doesn’t work at all and then when i do it individually i have about a 20 – 30% success rate. I usually end up with a timed out screen and when I head back to media library it shows “ERROR: posting to Smush.it”.
I have increased the Smush.it response time in Settings to 300 but no joy. I also enabled debug processing but no error messages other than “ERROR: posting to Smush.it”
Thanks
Kelly