How old is the house + panel + meter-box + incoming-wires ? We await your story/resolution.
If you end up doing/needing a new panel, maybe even meter box and feed wires....
...make sure conduits,etc (if like mine, panel IN-house, just a meter box and upstream exposed to weather) are puttied/insulated super good. Though this is perhaps an insultingly obvious warning (insulate/putty,etc)... but seems like something to fret (if corroded, was it a moisture problem?).
I'm just a DIY homeowner, but I got my licensed contractor friends to replace panel + meter box +more, and do it right. I believe, for a prior MA house... 1989-built house but the panel had issues by 2010...no entire-home-flickering/etc issues, i forget which circuit got me looking deep in panel but one breaker was warm so I pulled a few others too. Issue(s): a handful of corroded breaker contact areas on lower bus positions....pitting grey metal (no longer smooth) on some bus bar areas.. of course breaker's contacts will suffer, get warm, show results of arcing but I blamed the bus bar. Never really proved where corrosion started...inside panel, top area(feed) dry+good...bottom breakers also dry but some pitted! So I never solved that mystery of why did it degrade ... had to assume something like storm-rain-seeping so minor I had no indication in basement.
But as told above I DID get a new panel, new feed wires, attached pic shows (top) putty sealing the conduit to meter box, then there's a can't-see hole in the house wall, behind which in basement (INSIDE) is the panel. Panel/breakers 5-6ft above floor in a very dry and not-prone-to-humidity basement (foundation/cement-walls never leaked). Typical setup/design I assume...I've seen worse-looking setups lasting way more than 20 years!...such as....
My gf has a near-beach (1/4mi, just far enough away to avoid ocean salt air) Maine summer cottage with an OUTSIDE-HOUSE main panel. I just added a new circuit+breaker, yesterday was first time I removed the "dead front" shielded by a cover panel..it must be around 50 years old, but still good and minimal cobwebs, no dead or live bugs, amazing! You can bet I lightly filed/sanded the bus bar points for the bottom positions including the ones that were vacant. I didn't get them to be shiny grey metal, but they felt smooth enough. (NO PIC on that story.)