While QoS testing on this platform, unexpected QoS remarking behaviors were observed where any unlabeled traffic was getting DSCP values remarked and ECN ECT and CE bits set inconsistently. This was seen after upgrading the router from 22.4R3.22-EVO to 23.2R2.21-EVO.

.

Root-Cause:
1) scripts sends v4, v6, exp traffic.
2) all 3 streams go out of same egress interface of family v4, v6, mpls
3) expectation is default exp rewrite, dscp preservation for mpls, L3 traffic.
4) issue is v4, v6 doesn't undergo dscp preservation, exp rewrite happens.

Model: ACX7100-48L, Junos: 23.2R2.21-EVO, Yocto: 3.0.2, Linux Kernel: 5.2.60-yocto-standard-g3c005ea
JUNOS-EVO OS 64-bit [junos-evo-install-acx-f-x86-64-23.2R2.21-EVO]

While QoS testing on this platform, unexpected QoS remarking behaviors were observed where any unlabeled traffic was getting DSCP values remarked, and ECN ECT and CE bits set inconsistently. This was seen after upgrading router from 22.4R3.22-EVO to 23.2R2.21-EVO. ACX7100 is able to support both exp+dscp BA classifiers.

DUT is on 22.4R3.22-EVO with a BA classifier for DSCP and MF classifier for EXP. The code was upgraded to 23.2R2.21-EVO.  The MF classifier was removed from bundle interfaces and the EXP classifier was added to the qos configurations. With these configurations applied we were getting very inconsistent remarking behaviors. We tested removing all QoS configurations from the router so only the junos-defaults were inherited. 
The router was then remarking all unlabeled IPV4 and IPV6 traffic to DSCP 0 ECT 0 and CE 0 which is not expected.

Rebooting the system may temporarily restore functionality. However, this is not a viable long-term solution as the issue may recur.
Deactivate and activate v4/v6 family on the interface.