queries stop using indexes

I have a table with 15 cols , there is an joint index on 5 of them

there are ~15million records in the table, and it gets heavy use via
update & insert

i recently noticed that after a day of use, the index is no longer
being respected in some/all queries and a seq scan on the table is used

i ran analyze, no change.
i ran vacuum analyze, no change.

i dropped the index, and recreated it -- its now used again.

this happened 3x already this week.

can anyone offer a suggestion?

// Jonathan Vanasco

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