400 Bad activity error on follows

Hi! First off, thanks for building and running mostr.pub, it's awesome!

I successfully followed some Nostr users via mostr.pub a while back from https://fed.brid.gy/, probably over a month ago. When I tried a couple more follows today though, they failed with HTTP 400 Bad activity. Full example activity below, sent at 12:39:37p PT today. One notable part is that it has a full object instead of just a bare id, maybe mostr changed its activity handling recently and that's no longer supported?

(I get the same 400 Bad activity error on Undo(Follow) activities, but afaik that's just not supported yet, #18.)

Thanks in advance!

{
  "@context": "https://www.w3.org/ns/activitystreams",
  "type": "Follow",
  "id": "https://fed.brid.gy/user/snarfed.org/following#2022-01-02T03:04:05-https://mostr.pub/users/7dcc73e9f32356da460ab01a9db54c7c8a082fb07db4ac2d44bc10608ef05cbe",
  "actor": "https://fed.brid.gy/snarfed.org",
  "object": {
    "@context": [
      "https://www.w3.org/ns/activitystreams",
      {
        "mostr": "http://mostr.pub/ns#",
        "Zap": "mostr:Zap",
        "nostr": "mostr:nostr"
      }
    ],
    "type": "Person",
    "id": "https://mostr.pub/users/7dcc73e9f32356da460ab01a9db54c7c8a082fb07db4ac2d44bc10608ef05cbe",
    "name": "snarfed",
    "preferredUsername": "7dcc73e9f32356da460ab01a9db54c7c8a082fb07db4ac2d44bc10608ef05cbe",
    "inbox": "https://mostr.pub/users/7dcc73e9f32356da460ab01a9db54c7c8a082fb07db4ac2d44bc10608ef05cbe/inbox",
    "followers": "https://mostr.pub/users/7dcc73e9f32356da460ab01a9db54c7c8a082fb07db4ac2d44bc10608ef05cbe/followers",
    "following": "https://mostr.pub/users/7dcc73e9f32356da460ab01a9db54c7c8a082fb07db4ac2d44bc10608ef05cbe/following",
    "outbox": "https://mostr.pub/users/7dcc73e9f32356da460ab01a9db54c7c8a082fb07db4ac2d44bc10608ef05cbe/outbox",
    "icon": {
      "type": "Image",
      "url": "https://snarfed.org/ryan_profile_square.jpg"
    },
    "summary": "<a href=\"https://snarfed.org/\">https://snarfed.org/</a>",
    "attachment": [],
    "publicKey": {
      "id": "https://mostr.pub/users/7dcc73e9f32356da460ab01a9db54c7c8a082fb07db4ac2d44bc10608ef05cbe#main-key",
      "owner": "https://mostr.pub/users/7dcc73e9f32356da460ab01a9db54c7c8a082fb07db4ac2d44bc10608ef05cbe",
      "publicKeyPem": "-----BEGIN PUBLIC KEY-----\nMIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDIjEtXIWyIlRD7bKU4TFQ5RYrcZXl2WUqz5ny/yfc9Y+CADESUj/TSp6vaPpBIfVXEGFB5P7W4SAQpcJRkbQFh4Az9FuFkIyacqgT6/NNKAjZTiNy6Da9Vp8kJR/GE7fuo9M8LpCaVd5OCpmebjI3oKqLgq2DBqdo4IcWXhdC2IQIDAQAB\n-----END PUBLIC KEY-----"
    },
    "endpoints": {
      "sharedInbox": "https://mostr.pub/inbox"
    },
    "nostr": {
      "id": "babcf198402368c061f3b53b73eb276e1d91154602a917eaf3f074e351bdf431",
      "pubkey": "7dcc73e9f32356da460ab01a9db54c7c8a082fb07db4ac2d44bc10608ef05cbe"
    }
  },
  "to": [
    "https://www.w3.org/ns/activitystreams#Public"
  ]
}