An AppleScript error occurred

Every single SpamSieve action times out with the following:

Mail got an error: AppleEvent timed out.

near:

	<unknown location>
	Date Logged:	Today at 9:55:16 AM

	SpamSieve:	3.1.2 at /Applications/SpamSieve.app
	Device:	macOS 15.4.1 (24E263) on <redact>.local (MacBookPro18,1)
	User:	<redact>
	Language:	English

	Error:	<NSError Domain=NSOSStatusErrorDomain Code=-1712 UserInfo={
    MJTScriptArgumentsDescription = "<NSAppleEventDescriptor: [ 0 ]>",
    MJTScriptSubroutine = "listinboxestocheck",
    MJTStackFrames = (
        "-[NSAppleScript(MJT) mjtCallSubroutine:arguments:error:] (174)"
        ),
    NSAppleScriptErrorAppName = "Mail",
    NSAppleScriptErrorBriefMessage = "AppleEvent timed out.",
    NSAppleScriptErrorMessage = "Mail got an error: AppleEvent timed out.",
    NSAppleScriptErrorNumber = -1712,
    NSAppleScriptErrorRange = NSRange: {0, 0},
    NSLocalizedDescription = "An AppleScript error occurred.",
    NSLocalizedFailureReason = "Mail got an error: AppleEvent timed out.",
    NSLocalizedRecoverySuggestion = "Mail encountered error -1712 (errAETimeout - the AppleEvent timed out):
        
        	Mail got an error: AppleEvent timed out.
        
        near:
        
        	<unknown location>"
    }>

I read other posts on the forum and increased the timeout to 30 seconds, and everything still times out.

SpamSieve Version: 3.1.2
Email Client: Apple Mail

It may help to restart your Mac. If Mail is still bogged down after that, I recommend checking Activity Monitor to see whether it has high CPU use and recording some samples from Mail when it’s timing out to see what it’s busy doing.