v19.0 upgrade risks

I have an update from 18.5 MR3 to 19.0. After that the LACP connection with SFP+ doesn't work anymore with my Dell S4048 switcht. I'm also waiting for an answer from support.

check for Auto Negotiation. Set it, if not set. 

Auto Negotiation is set.
LACP link with Firmware 18.5 MR3 works well.

You could try to disable it and check, if the Links are online or not. 

The Links are online. 
I have change the LAG at the Firewall from Auto-Negotiation to 10000 Full duplex -- >  The LACP link come up.

After then I change back the LAG interface to Auto-Negotiation. It works..


Then I restart the Firewall and no LACP Link come up.

The Links are online. 
I have change the LAG at the Firewall from Auto-Negotiation to 10000 Full duplex -- >  The LACP link come up.

After then I change back the LAG interface to Auto-Negotiation. It works..


Then I restart the Firewall and no LACP Link come up.

Yes of course. The auto negotiation is only happening when the interface is coming up. If you change it later you have a running config and nothing will happen until you do a reboot.