As the error above mentions, only one where clause should be mentioned as seen in the example below.
Syntax error query:
Get events fields avg(elapsedtime), min(elapsedtime), max(elapsedtime) where elapsedtime exists where starttime between '2018-12-10 0:0:0' and '2019-12-31 23:59:59' group by starttime bucketed by day show as anomalychart
Correct syntax:
Get events fields avg(elapsedtime), min(elapsedtime), max(elapsedtime) where elapsedtime exists and starttime between '2018-12-10 0:0:0' and '2019-12-31 23:59:59' group by starttime bucketed by day show as anomalychart