The cosmwasm/wasm/v1/contract/build_address endpoint is broken.
Most paths have /contract/{address}/query so build_address is colliding and the router is interpreting it as an address that can't be parsed.

Example query:
https://cosmos-api.stakeandrelax.net/cosmwasm/wasm/v1/contract/build_address?code_hash=4ee07a1474cb1429cfbdba98fb52ca2efc2fe8602f8e1978dbc3f45b71511ca9&creator_address=cosmos1pgerac2dwufp7mzs4403h3je9ld4vkqngjtgdx&salt=74657374696e67

Response:
{"code":2,"message":"decoding bech32 failed: invalid separator index -1","details":[]}