same probem for me when controlling iTunes over the scriptingbridge.
i'm using now the release version hihg sierra (macOS 10.13 (17A365))
my app is freezing for seconds and sometimes for minutes in the AESendMessage when this happens
the call stack trace looks like this
* thread #1, name = 'MeMyselfAndIAppMainThread', queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
frame #0: 0x00007fff68112e76 libsystem_kernel.dylib`mach_msg_trap + 10
frame #1: 0x00007fff68112390 libsystem_kernel.dylib`mach_msg + 60
frame #2: 0x00007fff40a6c475 CoreFoundation`__CFRunLoopServiceMachPort + 341
frame #3: 0x00007fff40a6b7c7 CoreFoundation`__CFRunLoopRun + 1783
frame #4: 0x00007fff40a6ae43 CoreFoundation`CFRunLoopRunSpecific + 483
frame #5: 0x00007fff41b648c8 AE`waitForReply(unsigned int, WaitForReplyElem*, unsigned int, unsigned int) + 708
frame #6: 0x00007fff41b38171 AE`AESendMessage + 2963
frame #7: 0x00007fff4c59ac64 ScriptingBridge`-[SBAppContext sendEvent:error:] + 78
frame #8: 0x00007fff4c5947db ScriptingBridge`-[SBObject sendEvent:id:parameters:] + 452
frame #9: 0x00007fff4c5a1bc7 ScriptingBridge`getter_thunk + 86
frame #10: 0x00007fff669f69f3 libffi.dylib`ffi_closure_unix64_inner + 487
frame #11: 0x00007fff669f60e6 libffi.dylib`ffi_closure_unix64 + 70
* frame #12: 0x0000000100092067 Smart Tunes`::-[CiTunesManager findTrackIn:byID:](self=0x0000604000105100, _cmd="findTrackIn:byID:", tracks=0x000060800002ae60, trackID="205A30AFCD5B73E4") at CiTunesManager.mm:189
frame #13: 0x0000000100093258 Smart Tunes`::-[CiTunesManager restoreItunesStateIfAllowed](self=0x0000604000105100, _cmd="restoreItunesStateIfAllowed") at CiTunesManager.mm:255
frame #14: 0x00000001000926d6 Smart Tunes`::__40-[CiTunesManager canPlayAgainDoRestore:]_block_invoke((null)=<unavailable>) at CiTunesManager.mm:216
frame #15: 0x0000000101211f1f libdispatch.dylib`_dispatch_client_callout + 8
frame #16: 0x00000001012265be libdispatch.dylib`_dispatch_continuation_pop + 940
frame #17: 0x000000010121461b libdispatch.dylib`_dispatch_source_invoke + 658
frame #18: 0x000000010121e1e7 libdispatch.dylib`_dispatch_main_queue_callback_4CF + 1135
frame #19: 0x00007fff40aa9869 CoreFoundation`__CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 9
frame #20: 0x00007fff40a6baea CoreFoundation`__CFRunLoopRun + 2586
frame #21: 0x00007fff40a6ae43 CoreFoundation`CFRunLoopRunSpecific + 483
frame #22: 0x00007fff3fd8a866 HIToolbox`RunCurrentEventLoopInMode + 286
frame #23: 0x00007fff3fd8a5d6 HIToolbox`ReceiveNextEventCommon + 613
frame #24: 0x00007fff3fd8a354 HIToolbox`_BlockUntilNextEventMatchingListInModeWithFilter + 64
frame #25: 0x00007fff3e08844f AppKit`_DPSNextEvent + 2085
frame #26: 0x00007fff3e81d508 AppKit`-[NSApplication(NSEvent) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] + 3044
frame #27: 0x00007fff3e07d25d AppKit`-[NSApplication run] + 764
frame #28: 0x00007fff3e04c3fe AppKit`NSApplicationMain + 804
any progress on this problem?
TIA!
Hofi