When I quit just about any FX app with cmd-Q I get this message in the console:

"CoreAnimation: warning, deleted thread with uncommitted CATransaction; set CA_DEBUG_TRANSACTIONS=1 in environment to log backtraces." Following the advice, I set that environment variable and I see:

CoreAnimation: warning, deleted thread with uncommitted CATransaction; created by:
0 QuartzCore 0x00007fff944a2b95 _ZN2CA11Transaction4pushEv + 219
1 QuartzCore 0x00007fff944a276d _ZN2CA11Transaction15ensure_implicitEv + 273
2 QuartzCore 0x00007fff944a98ab _ZN2CA5Layer13thread_flags_EPNS_11TransactionE + 37
3 QuartzCore 0x00007fff944a97e3 _ZN2CA5Layer4markEPNS_11TransactionEjj + 79
4 QuartzCore 0x00007fff944a974a _ZN2CA5Layer25set_needs_display_in_rectERK6CGRect + 392
5 QuartzCore 0x00007fff944a959f -[CALayer setNeedsDisplay] + 62
6 libglass.dylib 0x0000000169765021 -[GlassView3D end:] + 97
7 libglass.dylib 0x00000001697622ac Java_com_sun_glass_ui_mac_MacView__1end + 204
8 ??? 0x000000010df52f90 0x0 + 4529139600
9 ??? 0x000000010df47158 0x0 + 4529090904

I think this happens because cmd-Q pretty much stops a Cocoa app dead in its tracks with exit().