Error when resolving ticket

Hello.
I have done RT update to version 3.6.6 yesterday and now when I am resolving ticket an error message is recorded in a log file:
Error: unexpected end of header (/…/rt3/lib/RT/Template_Overlay.pm:339)
Nothing has been changed recently except yesterday’s update to the newer version.
Don’t understand what happened and don’t know how to deal with this error.
Many thank for help
J. Borgul

Proximo Ltd

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