Unable to get more file system space for nsrmmd.

Networker 9.1

We have a weekly backup for a client server with 1TB of data. The retention is 2 weeks.

Every once in a while the backup fails, please see log below.

One of the lines reads: Unable to get more file system space for nsrmmd.

QUESTION #1:  I googled that line but can't find any info about it, does it mean that the adv_file volume ran out of disk space, and that's why the backup is failing?

QUESTION #2: If that's the case (not enough disk space), I wonder why since an older backup is supposed to expire just before a new backup takes place, in theory there should be enough disk space.

Example:

Backup #1: Sunday, Oct 1 @ 11:59pm (retention until Oct 15 @ 11:59pm)
Backup #2: Sunday, Oct 8 @ 11:59pm (retention until Oct 22 @ 11:59pm)
Backup #3: Sunday, Oct 15 @ 11:59pm (retention until Oct 29 @ 11:59pm)

When Backup #3 starts, Backup #1 is already expired and should free up the space.

Any suggestions are very welcome!

=====================================================================
138851:save: 'Client05.domain.local:C:\' is being reset/promoted to level 'Full' as no backup is found.
138851:save: 'Client05.domain.local:D:\' is being reset/promoted to level 'Full' as no backup is found.
129292:save: Successfully established Client direct save session for save-set ID '4220853723' (Client05.domain.local:<3>D:\) with adv_file volume 'Weekly.001'.
129292:save: Successfully established Client direct save session for save-set ID '4204076507' (Client05.domain.local:<3>C:\) with adv_file volume 'Weekly.001'.
129292:save: Successfully established Client direct save session for save-set ID '4187299293' (Client05.domain.local:<2>D:\) with adv_file volume 'Weekly.001'.
129292:save: Successfully established Client direct save session for save-set ID '4170522077' (Client05.domain.local:<2>C:\) with adv_file volume 'Weekly.001'.
129292:save: Successfully established Client direct save session for save-set ID '4153744861' (Client05.domain.local:<1>D:\) with adv_file volume 'Weekly.001'.
129292:save: Successfully established Client direct save session for save-set ID '4136967645' (Client05.domain.local:<1>C:\) with adv_file volume 'Weekly.001'.
129292:save: Successfully established Client direct save session for save-set ID '4120190431' (Client05.domain.local:D:\) with adv_file volume 'Weekly.001'.
129292:save: Successfully established Client direct save session for save-set ID '4103413216' (Client05.domain.local:C:\) with adv_file volume 'Weekly.001'.
parallel save streams partial completed savetime=1670716894
parallel save streams partial completed savetime=1670716892
parallel save streams partial completed savetime=1670716890
parallel save streams partial completed savetime=1670716896
parallel save streams summary Client05.domain.local: C:\ level=full, 20 GB 00:30:33 239797 files
parallel save streams summary savetime=1670716896
122665:save: DPSS save point 'Client05.domain.local:D:\' is currently being saved and is now using an additional stream (unused client parallelism slot) from a finished save point. Its current stream count is 3.
122665:save: DPSS save point 'Client05.domain.local:D:\' is currently being saved and is now using an additional stream (unused client parallelism slot) from a finished save point. Its current stream count is 4.
86715:save: Unable to get more file system space for nsrmmd.
86698:save: File system has no more space for save-set ID '4153744861'.
74209:save: Quit signal received.
142169:save: Save-set ID '4153744861' (client 'Client05.domain.local': save-set '<1>D:\') is aborted.
125797:save: DPSS save point backup has timed out after 26 minutes of internal operation inactivity.
12/11/22 06:48:42.218764 pre_read_peek_block_timeout_retry() (tid:2): DPSS internal operation read pipe inactivity timeout after 25 minutes (actual 26 minutes), so aborting the backup
12/11/22 06:48:42.218764 find_idle_emitter() (tid:2): ERROR: Could not get Emitter
Do MBS: Unable to find an idle emitter.
125798:save: DPSS save point 'Client05.domain.local:D:\' has encountered a critical error.
parallel save streams summary Client05.domain.local: D:\ level=full, 0 KB 06:47:25 0 files
parallel save streams summary savetime=1670716895
129292:save: Successfully established Client direct save session for save-set ID '3247799651' (Client05.domain.local:\\?\VOLUME{212F9345-2EC1-00E5-854C-806E6F6E6963}\) with adv_file volume 'Weekly.001'.
Client05.domain.local: \\?\VOLUME{212F9345-2EC1-00E5-854C-806E6F6E6963}\ level=full, 15 MB 00:00:15 77 files
Completed savetime=1670741333
90015:save: The backup of VSS emit save set '\\?\VOLUME{212F9345-2EC1-00E5-854C-806E6F6E6963}\' succeeded.
94694:save: The backup of save set '\\?\VOLUME{212F9345-2EC1-00E5-854C-806E6F6E6963}\' succeeded.
99123:save: Handling an abort while processing Windows backup.
90117:save: Unable to perform the ASR backup: cannot obtain the VSS MBS status.

86024:save: Error occured while saving disaster recovery save sets.