You good people,
I'm afraid this will be an imprecise description of a problem, but maybe somebody had similar experience and found a fix.
I'm running a server (14.0.4a) solution under El Capitan with up to five clients at the same time. My clients are filling in an order form by selecting items in a portal and then hit an "order" button. It's rather simple. No images, just numbers. Most of the time this works just fine, but sometimes, mostly (but not exclusively) when my clients hit the "order" button, they get a beach ball for about 30 seconds and then filemaker will say that connection the server was lost (the server sees an error 51, client no longer responding) and upon reconnecting, the client will be notified for a couple of minutes when trying to edit the record that they cannot edit the current record, because it is currently being edited by another user. I can make sure that there isn't really another user editing the same record. To me it seems as though the user in logged in double for those couple of minutes. The major problem is that some changes of the user will not be saved. Sometimes it is only the status of the order, which is supposed to change with a script of the "order" button, that doesn't change, but sometimes they lose parts or all of the edits performed in the portal, even though each single portal row has been committed. This also happens to users which are set to be never disconnected upon idle.
Again, sorry for the poor description. I wish I was more of a network guy to be able to point to more technical details. What is really confusing me is that the problem occurs only occasionally, maybe once or twice a day, and that data from already committed records gets lost. My server, an iMac from 2007 is not the most powerful machine and it doesn't sit behind the most powerful internet connection, but I would only expect lags instead of connection drops as a consequence thereof.
I found some threads discussing connection loss with filemaker 12, but none of them seemed conclusive to my issues.
So far this only happened to clients connecting over WAN. One machine is running 14.0.5 on Mavericks, the other is an iPad with Filemaker Go. I'm at a loss whether to look at my server configuration, my solution, the client's machines or their internet connections (so far only problems over Wifi or 3G. As far as I know, none of my clients is using ethernet).
Any input is much appreciated.