I have OS3 and Pi-Star , side by side, receiving on the same frequency.
The Anytone AT-878UV sends a message to 268999 and it is decoded by the Pi-Star but not by the OS3 .
If I send the same message to 2683328 (my DMR-ID) or to 9999 the message is well decoded by both Pi-Star and OS3 .
If I send the message to any other DMR-ID, then OS3 never decodes it. The Pi-Star, on the other hand, always decodes it.

Follows the log from Pi-Star and OS3:

Pi-Star LOG :
M: 2021-01-08 10:58:15.802 DMR Slot 2, received RF Data Preamble CSBK (17 to follow) from CT1EIZ to 268999
M: 2021-01-08 10:58:15.896 DMR Slot 2, received RF Data Preamble CSBK (16 to follow) from CT1EIZ to 268999
M: 2021-01-08 10:58:15.948 DMR Slot 2, received RF Data Preamble CSBK (15 to follow) from CT1EIZ to 268999
M: 2021-01-08 10:58:16.001 DMR Slot 2, received RF Data Preamble CSBK (14 to follow) from CT1EIZ to 268999
M: 2021-01-08 10:58:16.059 DMR Slot 2, received RF Data Preamble CSBK (13 to follow) from CT1EIZ to 268999
M: 2021-01-08 10:58:16.111 DMR Slot 2, received RF Data Preamble CSBK (12 to follow) from CT1EIZ to 268999
M: 2021-01-08 10:58:16.164 DMR Slot 2, received RF Data Preamble CSBK (11 to follow) from CT1EIZ to 268999
M: 2021-01-08 10:58:16.222 DMR Slot 2, received RF Data Preamble CSBK (10 to follow) from CT1EIZ to 268999
M: 2021-01-08 10:58:16.287 DMR Slot 2, received RF Data Preamble CSBK (9 to follow) from CT1EIZ to 268999
M: 2021-01-08 10:58:16.393 DMR Slot 2, received RF data header from CT1EIZ to 268999, 8 blocks
M: 2021-01-08 10:58:16.822 DMR Slot 2, ended RF data transmission

OS3 Log :
10:58:13 dmrcalltracker[0]: got csbk preamble, blocks to follow: 18, data follows: 1
10:58:13 dmrcalltracker[0]: prv data call started, dst: 268999 src: 2683328 id: e07cfeb0f21e7e58
10:58:13 nvmm-csd: id 268999 not found
10:58:13 dmrcalltracker[0]: call ended, dur 0.0s ber 6.4% loss 0.0% rssi -43
10:58:13 homebrew-dmr [0]: call stopped
10:58:13 dmrcalltracker[0]: got csbk preamble, blocks to follow: 17, data follows: 1
10:58:13 dmrcalltracker[0]: prv data call started, dst: 268999 src: 2683328 id: 446a84b656cc0e86
10:58:13 nvmm-csd: id 268999 not found
10:58:13 dmrcalltracker[0]: call ended, dur 0.0s ber 8.3% loss 0.0% rssi -43
10:58:13 homebrew-dmr [0]: call stopped
10:58:13 dmrcalltracker[0]: got csbk preamble, blocks to follow: 14, data follows: 1
10:58:13 dmrcalltracker[0]: prv data call started, dst: 268999 src: 2683328 id: 22e4f41a847c0cb6
10:58:13 nvmm-csd: id 268999 not found
10:58:13 dmrcalltracker[0]: call ended, dur 0.0s ber 7.1% loss 0.0% rssi -31
10:58:13 homebrew-dmr [0]: call stopped
10:58:13 dmrcalltracker[0]: got csbk preamble, blocks to follow: 13, data follows: 1
10:58:13 dmrcalltracker[0]: prv data call started, dst: 268999 src: 2683328 id: ca06cc9a86ec44ac
10:58:13 nvmm-csd: id 268999 not found
10:58:13 dmrcalltracker[0]: call ended, dur 0.0s ber 4.2% loss 0.0% rssi -43
10:58:13 homebrew-dmr [0]: call stopped
10:58:13 dmrcalltracker[0]: got csbk preamble, blocks to follow: 12, data follows: 1
10:58:13 dmrcalltracker[0]: prv data call started, dst: 268999 src: 2683328 id: 900c34aeb0089c4e
10:58:13 nvmm-csd: id 268999 not found
10:58:13 dmrcalltracker[0]: call ended, dur 0.0s ber 9.5% loss 0.0% rssi -43
10:58:13 homebrew-dmr [0]: call stopped
10:58:13 dmrcalltracker[0]: got csbk preamble, blocks to follow: 11, data follows: 1
10:58:13 dmrcalltracker[0]: prv data call started, dst: 268999 src: 2683328 id: 0eb49af624ac8cd4
10:58:13 nvmm-csd: id 268999 not found
10:58:13 dmrcalltracker[0]: call ended, dur 0.0s ber 3.0% loss 0.0% rssi -43
10:58:13 homebrew-dmr [0]: call stopped
10:58:13 dmrcalltracker[0]: got csbk preamble, blocks to follow: 10, data follows: 1
10:58:13 dmrcalltracker[0]: prv data call started, dst: 268999 src: 2683328 id: a2a2d05016249c4c
10:58:13 nvmm-csd: id 268999 not found
10:58:13 dmrcalltracker[0]: call ended, dur 0.0s ber 9.1% loss 0.0% rssi -43
10:58:13 homebrew-dmr [0]: call stopped
10:58:14 dmrcalltracker[0]: got csbk preamble, blocks to follow: 9, data follows: 1
10:58:14 dmrcalltracker[0]: prv data call started, dst: 268999 src: 2683328 id: 1ac69a22027434ec
10:58:14 nvmm-csd: id 268999 not found
10:58:14 dmrcalltracker[0]: call ended, dur 0.0s ber 3.8% loss 0.0% rssi -43
10:58:14 homebrew-dmr [0]: call stopped
10:58:14 dmrcalltracker[0]: prv data call started, dst: 268999 src: 2683328 id: 0e98ca2ce4be7270
10:58:14 nvmm-csd: id 268999 not found
10:58:14 dmr-sms: sms call is not ongoing, ignoring rate 1/2 data
10:58:14 dmr-sms: sms call is not ongoing, ignoring rate 1/2 data
10:58:14 dmr-sms: sms call is not ongoing, ignoring rate 1/2 data
10:58:14 dmr-sms: sms call is not ongoing, ignoring rate 1/2 data
10:58:14 dmr-sms: sms call is not ongoing, ignoring rate 1/2 data
10:58:14 dmr-sms: sms call is not ongoing, ignoring rate 1/2 data
10:58:14 dmr-sms: sms call is not ongoing, ignoring rate 1/2 data
10:58:14 dmr-sms: sms call is not ongoing, ignoring rate 1/2 data