Layer 2 Fiber link having odd issues with VLAN 1 from Service Provider

Hoping you guys might be able to provide some insight on what the ISP is doing in this case that might be causing my problem.

So we use Cisco and have VLAN 1 as our native VLAN (I know shitty practice). We recently got a Layer 2 Fiber Uplink to a remote office. We realized DHCP isn't working across the link but routing works fine and all the correct IP Helpers on the SVI are added.

We have a redundant (different provider) link that works normally at this site and is also Layer 2 fiber up link. The only difference is that it is a direct fiber hand off and the link that is giving us trouble is using a fiber to Ethernet hand off.

After some troubleshooting with the provider and running a packet capture on the trunk link I discovered any kind of broadcast would come up with "Ethernet Frame Checksum Errors". If you google this you get alot of generic responses saying its just a wire shark error and to filter it out. As I dug deeper into the issue I noticed that STP is not working for VLAN 1 as well but for other VLANs it works normally (pointing to our core switches as the root) VLAN 1 seems to point to it self as the root. In the packet capture all the STP Frames for VLAN are bigger (94 bytes vs being 64 bytes for the other vlans) and it also comes up with the Ethernet Check Sum Error. I noticed that alot of the broadcasts are VLAN 1 related or somehow leverage it to some capacity. I worked with the SP on this and sent them all the packet captures and they did some monitoring on there end but they have not been helpful at all and tried some meaningless tests. I feel like they are doing some kind of extra tagging or filtering out VLAN1 in some way but they keep denying this and saying tagged and untagged traffic should pass normally. Q and Q is not needed per the ISP. I requested they remove the Ethernet hand off and just use direct fiber and also to open up a case with there equipment provider because somewhere along the lines this is not working properly on their end.

Anyone ever experience something like this or have an idea what the SP is doing? I feel like they are not giving me the full story. They are a small SP and after speaking with some of their onsite techs it seems this fiber to Ethernet hand off thing is new for them and they are trying to no do fiber only hand offs apparently.

In the meantime I am looking into other SP for this service. There support has been really unhelpful.