Bitcoind "Daemon:timeout error" - when connecting from built-in ElectrumX fragment

[maltokyo]

Recently, after a restart, I keep getting ERROR:Daemon:timeout error. Retrying occasionally... in the electrumx logs, but it happens minutes after the INFO:Daemon:running normally log entry, so there is no issue with the connection from electrumx to bitcoind... my setup has been running fine for years, so no idea what is happening here. Any way to debug or find root cause? I have spent hours and am at a loss. Thanks!

Full log... and the last line just keeps being output endlessly.

INFO:electrumx:ElectrumX server starting
INFO:electrumx:logging level: DEBUG
INFO:Controller:Python version: 3.7.9 (default, Dec 18 2020, 05:56:48)  [GCC 9.3.0]
INFO:Controller:software version: ElectrumX 1.16.0
INFO:Controller:aiorpcX version: 0.18.7
INFO:Controller:supported protocol versions: 1.4-1.4.2
INFO:Controller:event loop policy: <uvloop.EventLoopPolicy object at 0x7f46ebf80b10>
INFO:Controller:reorg limit is 200 blocks
INFO:Daemon:daemon #1 at bitcoind:43782/ (current)
INFO:DB:switching current directory to /data
INFO:DB:using leveldb for DB backend
ERROR:Daemon:starting up checking blocks.  Retrying occasionally...
INFO:Daemon:running normally
INFO:DB:opened UTXO DB (for sync: True)
INFO:DB:UTXO DB version: 8
INFO:DB:coin: BitcoinSegwit
INFO:DB:network: mainnet
INFO:DB:height: 674,020
INFO:DB:tip: 0000000000000000000b462f7608771b5bfb262457fb5e9cce31adf5fff7579e
INFO:DB:tx count: 623,533,309
INFO:DB:flushing DB cache at 4,000 MB
INFO:DB:sync time so far: 14h 01m 41s
INFO:History:history DB version: 1
INFO:History:flush count: 285
INFO:SessionManager:RPC server listening on 0.0.0.0:8000
INFO:Prefetcher:catching up to daemon height 868,651 (194,631 blocks behind)
ERROR:Daemon:timeout error.  Retrying occasionally...
ERROR:Daemon:timeout error.  Retrying occasionally...
ERROR:Daemon:timeout error.  Retrying occasionally...
ERROR:Daemon:timeout error.  Retrying occasionally...
ERROR:Daemon:timeout error.  Retrying occasionally...
ERROR:Daemon:timeout error.  Retrying occasionally...
ERROR:Daemon:timeout error.  Retrying occasionally...