ASSERT on detach dispatch.c:714 false

On detach in a modified api.static_signal test on iter 524 out of 1000:

524
Sending SIGUSR1 pre-DR-init
Got SIGUSR1
pre-DR init
<Starting application /home/bruening/dr/git/build_x64_dbg_tests/suite/tests/bin/api.static_signal (6656)>
<unable to determine lib path for cross-arch execve>
<Initial options = -stack_size 56K -max_elide_jmp 0 -max_elide_call 0 -no_inline_ignored_syscalls -native_exec_default_list '' -no_native_exec_managed_code -no_indcall2direct >
in dr_client_main
Sending SIGUSR1 pre-DR-start
Got SIGUSR1
pre-DR start
<Attached to 2 threads in application /home/bruening/dr/git/build_x64_dbg_tests/suite/tests/bin/api.static_signal (6656)>
Sending SIGUSR1 under DR
Got SIGUSR1
pre-raise SIGSEGV under DR
Got SIGSEGV
pre-DR stop
<Application /home/bruening/dr/git/build_x64_dbg_tests/suite/tests/bin/api.static_signal (6656).  Internal Error: DynamoRIO debug check failure: /home/bruening/dr/git/src/core/dispatch.c:714 false
(Error occurred @596 frags)
version 6.2.17250, custom build
-stack_size 56K -max_elide_jmp 0 -max_elide_call 0 -no_inline_ignored_syscalls -native_exec_default_list '' -no_native_exec_managed_code -no_indcall2direct 
0x000000004e19ac10 0x00000000004fb21e
0x000000004e19ae50 0x00000000004e6dd7
0x000000004e19aee0 0x00000000004e5ca6
0x000000004e19af10 0x00000000004e3851
0x000000004e19aff0 0x000000004e122ec5
0x00007ffea0329f70 0x00007f19d6ffef45>
FAILURE

So dispatch_enter_native failed: returned from enter_fcache. ??