2819480 - Execution of DBCC USEDEXTENTS in parallel crashes ASE when trace flags 1631 and 1633 are enabled

Two "DBCC USEDEXTENTS" (different databases) executing at the same time crashes ASE with signal 11 when trace flags 1631 and 1633 are enabled. We can see the following stacks:

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1) Signal 11 at buf_sign_pgarray

....
....
Run to completion task iocRunController(NNNNNN) exception 11
nthrd_backtrace
krtctskException
kisignal
buf_sign_pgarray
brfinish
sdfinish_normal
sddone_normal
blkioComplete
kdcProcessCompletions
udcPoll
iocRunController
krtctskRun
ktskRun
kt__RTCMain
thread_create_handler

2) Signal 11 at dbts_ptscmp

...
...
Spinlocks held by taskblock 1000067a608
Spinlock default data cache at address 00000100004fd8NN owned by NNNNNNNNNN
End of spinlock display.
Run to completion task iocRunController(NNNNNN) exception 11
nthrd_backtrace
krtctskException
kisignal
dbts_ptscmp
brfinish
sdfinish_normal

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When disabling trace flags then we can see a spurious error 823 when executing two command at the same time:

Error: 823, Severity: 24, State: 1
server I/O error detected during read for BUF=BBBBBBBBBBBB, MASS=MMMMMMMMMMMM, Buf#=0, page=PPPPPPPPPP, dbid=NN, Mass vdevno=NNN, vpage=NNNNNN, Buf lpage=NNNN,
Mass stat=NNNNN, Buf stat=0000, size=2048, cid=0 ('default data cache'), Pinned xdes=0x0000000000000000, spid=0.

• SAP Adaptive Server Enterprise (ASE) 16.0 SP02 PL08 

buf_sign_pgarray brfinish sdfinish_normal sddone_normal blkioComplete kdcProcessCompletion dbts_ptscmp dbcc usedextents parallel crash spinlock iocRunController taskblock traceflags trace flags 1631 1633 , KBA , BC-SYB-ASE , Sybase ASE Database Platform (non Business Suite) , Problem