Since upgrade to 18.1 Webaccess (3 instances/Servers) stops autorefreshing the browser after about 20min to 60 minutes.
slap polling from the poa are still received:

webaccess log (diagnostic):
14:27:04, <SOAP>, -, INFO, USERID, POLLING: Slap received for session sequence #49

in webaccess admin interface:
User Id Logged In Last Access Last Slap (GC) Last Slap (POA) Interface Domain Post Office Language Client IP Session Sequence Browser
email 11/20/18 13:32 11/20/18 14:27 N/A 11/20/18 14:27 css Domain poa de ipaddress 49 Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:63.0) Gecko/20100101 Firefox/63.0

as you can see last slap (Poa) is received, but the webaccess browser does not refresh.
New login does not help, and affects all users also new ones.

restarting tomcat resolves the problem, but only for max one hour. (maybe depends on the amount of users?)