This is just ruining the game.

It's beyond normal. You have no control over the variables. As usual you are given no information behind the mechanics of the issue nor are you given any tools to rectify it.

Stinks of bug or bad design.

Yep.
I'm trying to sell anyone rated 70 or over for my current career mode - and just can't get shot of Ndong.  Have accepted multiple bids of 12.5m only to see negotiations break down.  Sold Lens, Khazri, Borini, Djilobodji, Cattermole, Kone, Rodwell, etc., for decent money and all deals went through, but Ndong's just keep collapsing.  I've even started accepting lower bids for him now in case it's the fee that is killing the deal.

between this is the questionable AI squad selections the game is really fkd.

I think this is the worst FIFA they have ever made. The gameplay is disgraceful. The focus so much on tricks and shit and not play proper football. Too many easy goals and shit defenders make it un enjoyable

Agree - it's a big step-down from previous editions.  Found it frustrating to get used to the new game engine, but once I'd cracked how to play it's become a challenge to actually make the game a challenge.  Previous versions I've struggled to finish in the top of the Premier League without altering a couple of sliders a little in my favour - right now I've got 8 points from 5 games with a team of u70 rated players.

i like that they slowed it down a little. 

Slowing it down was important because they have made passing a more important part of the game and reduced the benefit of having a super-fast striker.  They've also made crossing/heading too easy.  It was a bastard in 17, but it's waaaaay too easy to thump a header home now.

I like that they have made players more accident prone now - I've noticed quite a few passes (especially from keeper to defender) that go just wide enough to put the defender off balance.  First time it happened I almost kicked the tv in, but having got used to it now I pay a little more attention to WHO is passing the ball to WHO.

To all points here so far. The slowing was a godsend. Had CPU defenders stopping for my through balls and just cut the line every time as my guys were so fast.

Weirdly my transfers get accepted on deadline day. All green ticks and the player is still in my squad and no money. It says the player is ready to join his teammates. 

the keeper passes are horrible.  every keeper is suddenly claudio bravo giving away free shots on goal.

can't believe you found headers easier. last year i was picking up a goal from a corner every 2 or 3 games. im lucky to get one in a season now.

i have about 8 players transfers break down in this latest career ive started.  some of them 3 or 4 times.

i do like that bids can be made outside of the transfer period now though.

Headers from open play - easier.  Overlapping full backs crossing for a bullet header, etc.

From corners - harder.  Used to go for an in-swinger to the front post and score 7-8 from corners per season.  Think I got about 3 in my last full season.

The offer might be accepted inside the deadline, but it always takes a couple of hours/days for the player to agree to the deal, so he ends up on your books and available to use until the next window.