Mutler hangs on third file

I am using request to upload formData. 90% of the time everything is ok but.. on this 10% multer hangs on third file. If i repeat the request everything will be fine. I've checked that third file is not even processed in filefilter/filename functions. Multer just hangs always after processing only 2 files. There are no errors on both sides (request and express), only 60s timeout in haproxy after node doesn't respond on side with multer.
Any thoughts.. ? As i said if i repeat the request everything goes ok. In request i am using 3 readstreams for the files.