Having trouble in fleet

He may be refreshing attempts for the 50 crystals. Or he has a friend who is also attacking you.  

If you can get to second place without any hassle that might be a saner approach.  If there is a shard chat try to get into it. 

So he's attacking me, forfeiting, paying 50, then attacking me again just to be sure to take 1st?

You can basically lock someone around for about 6 to 7 minutes even though the battle only last 5.  I forget the exact mechanics, but it relies on starting the battle, going into airplane mode, the force killing the app. You can't log back in after this for a few minutes (I don't remember if that is the exact method, but it is similar to that, been a while since i had to do it since I'm not in a highly competitive shard anymore).  

The game is designed so that you don't have to be connected to the internet for the entire battle, only starting the battle and at the end to report the results.  But if you have spotty internet, they have designed some flexibility in that end report.  And while it is waiting for the end report from your device, the game will still consider you to be "in battle" and will not allow you to finish.  So the concept is that if you turn off internet and force close, you device can't report on the end of the battle, so the game will wait a long as possible, past the 5 minute timer for you to report back.  If you never report back, the game finally decides the battle was a time out and releases the lock (this is the grace period which is 1 to 2 minutes).  

So how is this working if your opponent is also beating you?  Well, not sure if that is possible, so might be multiple people involved as others have suggested.  But you can abuse the above idea (assuming you can confirm the exact mechanics of it) to try to lock your opponent out sooner than 7:30 before payout.

The eaiser method - have you tried reaching out to them to find out  what's going on?  Maybe there is an arena shard chat you can join?  Or alternative, change your payout to soemthing less competitive?

Yes, it is a possibility that he attacks, lets it time out and then pays crystals to do it again.  

If you can't find a shard chat you can try to message him in game and propose rotating who gets first place.  

I'd be surprised if there is any ship shard that isn't run by a group (shard mafia); this is the way.  It looks to me they're deliberately halting your run for some reason.  Your best bet is to approach players that you think would be part of this group/mafia and be very very nice. You need to show you can be a team player.

Be aware though, shard mafias are real 'Lord of the Flies'.  Everything is done on discord and it is self-policed.  You may get lucky, and have real gems.  You may get unlucky and have the B-cast from the Sopranos.  

All I can advise is that you contact them, say you're willing to what's needed, and tread on those egg shells like they were made out of........hmmmm the shells of eggs!

So could be he's abusing airplane mode to extend the timeout but not so long as to get timed out himself. Man that's scummy.

I voluntarily take 2nd daily.  It’s 25 crystals difference, I don’t care about the prestige and it makes things easy.  I used to snipe back and forth but it wasn’t worth the effort and aggravation, the shard I’m in is ancient and not very active any more so it’s pretty civilized now.  

There's a possibility that you've been unintentionally screwing up the payouts for others, either a hard core shard mafia or a relaxed one getting very annoyed. If it's always the same person, search for them on swgoh.gg to find their payout, if it's the same as yours then you might be as frustrating for them.