My factory-reset HP48GX hangs when there's more than a few stack items

Hi. My rather old ebay-acquired HP48GX 128k has been great but lately hangs up (hour glass symbol) when I have a few dozen items on the stack, or randomly when doing any calculation. I've reset the machine every way I know how and left batteries out for months. No change. Is this a thing? Dry caps near memory chips? Impossible to open without breaking I think. Would be glad to know I'm not alone. Any info? Ta very much.