Lost HABpanel due to "Method failed: HTTP/1.1 503 Service Not Available" due to Foscam hang

My Foscam camera sometimes freezes and stops respond. In case it occurs I get the following message in openhab.log:
[WARN ] [org.openhab.io.net.http.HttpUtil ] - Method failed: HTTP/1.1 503 Service Not Available

However this issue causes the whole HABpanel stops work i.e. widgets are not visible and panels remain blank (black). It looks like HABpanel (and also HABmin) stops resolving items.

My Foscam item looks like below:
String Foscam_Motion2_Room “Motion detection [%s]” (gOchrona) { http="<[*)]" }