Electrs Server not synching panicking on Segwit Block

Support and Troubleshooting
1

Hi,

I cannot get Electrs to work, it repeatedly finds a bad block, most probably in my copy of the blockchain. Most probably i would need to re-download the blockchain. Would that be possible and how ?

I repeatedly restarted umbrel deleted electrs files and so on, deleted electrs app and re-installed it, but to no avail.

Any help would be appreciated

Log file goes as follows

Starting electrs 0.10.9 on x86_64 linux with Config { network: Bitcoin, db_path: “/data/db/bitcoin”, db_log_dir: None, db_parallelism: 1, daemon_auth: CookieFile(“/data/.bitcoin/.cookie”), daemon_rpc_addr: 10.21.21.8:8332, daemon_p2p_addr: 10.21.21.8:8333, electrum_rpc_addr: 0.0.0.0:50001, monitoring_addr: 127.0.0.1:4224, wait_duration: 10s, jsonrpc_timeout: 15s, index_batch_size: 10, index_lookup_limit: None, reindex_last_blocks: 0, auto_reindex: true, ignore_mempool: false, sync_once: false, skip_block_download_wait: false, disable_electrum_rpc: false, server_banner: “Umbrel Electrs (0.10.9)”, signet_magic: f9beb4d9 } electrs_electrs_1 | [2025-08-24T15:41:23.917Z INFO electrs::metrics::metrics_impl] serving Prometheus metrics on 127.0.0.1:4224 electrs_electrs_1 | [2025-08-24T15:41:23.917Z INFO electrs::server] serving Electrum RPC on 0.0.0.0:50001 electrs_electrs_1 | [2025-08-24T15:41:24.053Z INFO electrs::db] “/data/db/bitcoin”: 606 SST files, 47.418287575 GB, 3.895516313 Grows electrs_electrs_1 | [2025-08-24T15:41:24.680Z INFO electrs::chain] loading 697480 headers, tip=0000000000000000000352194836112f5f38266a4c733351e817c3b31bf510b6 electrs_electrs_1 | [2025-08-24T15:41:25.236Z INFO electrs::chain] chain updated: tip=0000000000000000000352194836112f5f38266a4c733351e817c3b31bf510b6, height=697480 electrs_electrs_1 | [2025-08-24T15:41:25.287Z INFO electrs::index] indexing 2000 blocks: [697481..699480] electrs_electrs_1 | thread ‘index_build’ panicked at ‘core returned invalid block: UnknownSegwitFlag(0)’, src/index.rs:317

2

Yes, it is possible to have your Bitcoin node double-check its timechain data. There is a quick version and full version - maybe try the quick one first, and if it doesn’t work, move on to the full one.

I offered some notes and a screenshot for how to do it here: Re-indexing timechain data

1 Like
3

Turned out i had a bad block which went unnoticed since i did not use Electrum up to this time. I had to reindex the blockchain after that, everything works fine. Thank you