1. What could be triggering this error?
RPC commands are being issued faster than they can be handled.
2. What can I do to avoid it? Settings recommended [ DO NOT POST SESC LINKS ]here[/url] fix it or just delay the problem?
You can set -rpcworkqueue to a number higher than 16.
3. Is there a log or a command that allows me to query and monitor the number and origin of RPC quests over time?
Start bitcoind with -debug=rpc and -debug=http. You will see information about the RPC commands and HTTP server stuff logged to the debug.log file.