actually I just found it: here it is...
Error log timestamp Saturday 03/06/23 10:13:32 PM
Runtime error: "syntaxError" not understood
MessageNotUnderstood>>defaultAction
MessageNotUnderstood(Exception)>>activateHandler: <anUndefinedObject>
MessageNotUnderstood(Exception)>>handle
MessageNotUnderstood(Exception)>>signal
MessageNotUnderstood class>>message: <aMessage>
LetCommand(Object)>>doesNotUnderstand: <aMessage>
LetCommand(BasicCommand)>>nextTokenClosesParens: <anOrderedCollection>
LetCommand>>using: <anOrderedCollection>
BasicCompiler>>parseNext
BasicCompiler class>>compileFromString: <'
...'> notify: <aBasicSourcePane>
BasicCompiler class>>compileFromString: <'
...'> notify: <aBasicSourcePane> ifSuccess: <aBlockClosure>
BasicSourcePane>>run
BasicSourceWindow>>run
BasicSourceWindow(Object)>>perform: <#run>
MenuWindow>>performMenuItem: <1281>
BasicSourceTopPane(ApplicationWindow)>>performMenuItem: <1281>
Message>>perform
NotificationManager>>empty
NotificationManager>>runPendingEvents
NotificationManager>>runEventLoop
Message>>perform
Message>>evaluate
Process>>safelyEvaluate: <aMessage>
Process>>evaluate: <aMessage>
well at least I discovered its hiding place.
It was in C:\Program Files (x86)\Liberty BASIC v4.5.1 in the file 'error' - not where it was supposed to be?