FXO calls disconnect: fxols_line_reversal_clid_wait. On_hook line reversal detected possibily due to crossed cable

Customer running CME on c2800nm-advipservicesk9-mz.124-4.XC4.bin with 6 FXO ports on 2 VWIC2-4FXO cards.  The complaint was that callers in conversation with outside parties disconnect at random times.  The duration of the call and destination didn't seem to matter.

Running "debug voip ccapi inout" and "debug vpm all" to investigate, occasionally found the following:

Nov 22 13:06:39: htsp_process_event: [0/1/0, FXOLS_ONHOOK, E_DSP_SIG_0110]

Nov 22 13:06:39: fxols_line_reversal_clid_wait. On_hook line reversal detected possibily
due to crossed cable
Nov 22 13:06:39: htsp_process_event: [0/1/1, FXOLS_ONHOOK, E_DSP_SIG_0110]
Nov 22 13:06:39: fxols_line_reversal_clid_wait. On_hook line reversal detected possibily
due to crossed cable
Nov 22 13:06:39: htsp_process_event: [0/1/2, FXOLS_ONHOOK, E_DSP_SIG_0110]
Nov 22 13:06:39: fxols_line_reversal_clid_wait. On_hook line reversal detected possibily
due to crossed cable
Nov 22 13:06:39: htsp_process_event: [0/1/3, FXOLS_ONHOOK, E_DSP_SIG_0110]

To confirm this was not a crossed cable or a flip in tip and ring leads, cables were inspected. No physical layer changes were made in years.

To confirm the issue was not related to the FXO card (errors were only related to one card), I swapped the two card positions in the router.  The errors above continued to happen on the same ports (0/1/X), ruling out a card failure.

Running "show voice dsp group all" indicated the DSPs were up and looked normal.

DSP groups on slot 0:

dsp 1:
State: UP, firmware: 8.4.1
Max signal/voice channel: 16/16
Max credits: 240
Group: FLEX_GROUP_VOICE, complexity: FLEX
Shared credits: 240, reserved credits: 0
Signaling channels allocated: 12
Voice channels allocated: 0
Credits used: 0

dsp 5:
State: UP, firmware: 8.4.1
Max signal/voice channel: 16/16
Max credits: 240
Group: FLEX_GROUP_VOICE, complexity: FLEX
Shared credits: 240, reserved credits: 0
Signaling channels allocated: 0
Voice channels allocated: 0
Credits used: 0
Tracing physical cables further, I found the 4 ports in question were served by an Adtran Total Access 616, while the other 2 appeared to be standard POTS lines.  In discussions with the TELCO carrier, errors on the T1 serving the Adtran were found and remote access to the device was not possible.

A site visit by a carrier representative indicated "this thing is toast" and the Adtran was replaced.

Problem solved.