On my OF3.3.3 and Spark 2.5.7 and 2.5.8 I see the following problem: Whenever any chat packet gets sent to the other end right between one user tries to send a file but the other end has not yet accepted the file transfer or OF determines the best method the whole transfer fails!
So it looks like a component (Spark OR Openfire?) gets disturbed by the fact that the next packet after a file transfer request is NOT a Accept/Decline but rather a “normal” chat packet.
The only way of getting reliabe file transfers (besides the other issues I have reported here but nobody picked up so far) is, to NOT touch the keyboard as long as there is a file transfer pending besides clicking accept for the receiver and not doing anything til the transfer starts for the sender.
As you can imagine this is very hard to get into the users as even the typing notification causes the transfer not to start…
Can anybody confirm this?