Postgres: cache lookup failed for type 5308416

When inserting data into a Postgres (timescaledb hyper)table, the following error occurs approximately every 1-5 seconds.

ERROR:  cache lookup failed for type 5308416

I'm attempting to find what this type is in order to debug further. I've tried looking in the following places but all return zero results:

select * from pg_class where oid = 5308416;
select * from pg_collation where oid = 5308416;
select * from pg_ts_config where oid = 5308416;
select * from pg_ts_dict where oid = 5308416;
select * from pg_namespace where oid = 5308416;
select * from pg_operator where oid = 5308416;
select * from pg_proc where oid = 5308416;
select * from pg_type where oid = 5308416;

The query I'm running looks as follows:

INSERT INTO "import" AS "T"
  ("a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z", "aa", "ab", "ac", "ad", "ae", "af", "ag", "ah", "ai", "aj", "ak", "al", "am", "an", "ao", "ap", "aq", "ar", "as", "at", "au", "av", "aw", "ax", "ay", "az", "ba", "bb") 
VALUES
  ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15, $16, $17, $18, $19, $20, $21, $22, $23, $24, $25, $26, $27, $28, $29, $30, $31, $32, $33, $34, $35, $36, $37, $38, $39, $40, $41, $42, $43, $44, $45, $46, $47, $48, $49, $50, $51, $52, $53, $54),
  ($55, $56, $57, $58, $59, $60, $61, $62, $63, $64, $65, $66, $67, $68, $69, $70, $71, $72, $73, $74, $75, $76, $77, $78, $79, $80, $81, $82, $83, $84, $85, $86, $87, $88, $89, $90, $91, $92, $93, $94, $95, $96, $97, $98, $99, $100, $101, $102, $103, $104, $105, $106, $107, $108),
  -- omitted 22 statements
  ($1297, $1298, $1299, $1300, $1301, $1302, $1303, $1304, $1305, $1306, $1307, $1308, $1309, $1310, $1311, $1312, $1313, $1314, $1315, $1316, $1317, $1318, $1319, $1320, $1321, $1322, $1323, $1324, $1325, $1326, $1327, $1328, $1329, $1330, $1331, $1332, $1333, $1334, $1335, $1336, $1337, $1338, $1339, $1340, $1341, $1342, $1343, $1344, $1345, $1346, $1347, $1348, $1349, $1350)
ON CONFLICT ("a", "b", "c", "d") DO NOTHING

When retried, the statement inserts as expected. Where should I look to find the referenced type 5308416? This type number is consistent in the logs over several days. For clarity, this is running from a dotnet 8 host, using npgsql.