I'm having a similar experience having used my own MIBs in the MIB folder.
ERRORS as follows:
time=2025-05-09T13:31:39.200Z level=INFO source=net_snmp.go:174 msg="Loading MIBs" from=mibs
time=2025-05-09T13:31:39.202Z level=WARN source=main.go:179 msg="NetSNMP reported parse error(s)" errors=56
time=2025-05-09T13:31:39.202Z level=ERROR source=main.go:185 msg="Missing MIB" mib=SNMPv2-TC from="At line 10 in mibs/WLC.mib"
time=2025-05-09T13:31:39.202Z level=ERROR source=main.go:185 msg="Missing MIB" mib=SNMPv2-TC from="At line 10 in mibs/WIFI.mib"
time=2025-05-09T13:31:39.202Z level=ERROR source=main.go:185 msg="Missing MIB" mib=SNMPv2-TC from="At line 10 in mibs/WAN.mib"
time=2025-05-09T13:31:39.202Z level=ERROR source=main.go:185 msg="Missing MIB" mib=SNMPv2-TC from="At line 10 in mibs/SFP.mib"
time=2025-05-09T13:31:39.202Z level=ERROR source=main.go:185 msg="Missing MIB" mib=SNMPv2-TC from="At line 10 in mibs/PEPVPN-SPEEDFUSION.mib"
time=2025-05-09T13:31:39.202Z level=ERROR source=main.go:185 msg="Missing MIB" mib=SNMPv2-TC from="At line 10 in mibs/LAN.mib"
time=2025-05-09T13:31:39.202Z level=ERROR source=main.go:185 msg="Missing MIB" mib=HCNUM-TC from="At line 12 in mibs/IPT-NETFLOW-MIB.my"
time=2025-05-09T13:31:39.202Z level=ERROR source=main.go:185 msg="Missing MIB" mib=SNMPv2-TC from="At line 14 in mibs/IPT-NETFLOW-MIB.my"
time=2025-05-09T13:31:39.202Z level=ERROR source=main.go:185 msg="Missing MIB" mib=SNMPv2-TC from="At line 9 in mibs/IPSEC-VPN.mib"
time=2025-05-09T13:31:39.202Z level=ERROR source=main.go:185 msg="Missing MIB" mib=SNMPv2-TC from="At line 10 in mibs/GRE.mib"
time=2025-05-09T13:31:39.202Z level=ERROR source=main.go:185 msg="Missing MIB" mib=SNMPv2-TC from="At line 10 in mibs/DEVICE.mib"
time=2025-05-09T13:31:39.202Z level=ERROR source=main.go:185 msg="Missing MIB" mib=SNMPv2-TC from="At line 10 in mibs/CELLULAR.mib"
time=2025-05-09T13:31:39.202Z level=ERROR source=main.go:137 msg="Failing on reported parse error(s)" help="Use 'generator parse_errors' command to see errors, --no-fail-on-parse-errors to ignore"
I downloaded the MIBs it said they were missing into the MIBs folder on the French site, but still no joy. Any guidance very much appreciated!.