Network vpnc hickups since 15.0 -> Tumbleweed

I have upgraded from Leap 15.0 to TW 20191004.
Since then the vpnc connection to the company network has hickups - meaning at some point in time I do not receive any TCP packets any more.
I used wireshark to debug the issue using “git pull” as my test program which simply hangs.
What I see is that after some normally exchanged packets the company host stops sending TCP ACK (or any packets) and my host keeps
resending TCP packets (retransmission) which will never be acknowledged.
The weird thing is that the connection partly works, e.g. opening a web page on a company server shows parts of the web page but at some
point hangs then forever.

I already tried to boot the old kernel from Leap 15.0, 4.12.14-lp150.12.73-default, with no luck. Problem still persist.
Booting a live Leap 15.1 KDE on the same machine shows also no problem (I see that the vpnc software version is the same in Leap 15.1 and TW,
so even this is to be ruled out I assume).
I never encountered a problem when not using the vpnc tunnel. “git pull” on e.g. etc. works fine

Any ideas what I can do to track down the problem ?

You’ll need to collect information about what is happening…
Did your VPN crash and restart, or is it stable but traffic stops?
You should see if anything is reported by the service “status”

systemctl status vpnc@client

There is an ArchWiki that contains some brief info and some troubleshooting hints.

And, you can leave open a console reading your system logs in real time to see what is being reported (of course start it before you initiate your vpn connection)

journalctl -f