It is a problem to hear your kids mispronounce words because sometimes it's so cute and funny you just let them do it. It would probably be easier on them to have me correct them than some college professor, but I love hearing them say things wrong.
Thing 1 seemed to grow out of doing this earlier than Thing 2 has.
Two that quickly come to mind are how Thing 2 says "lie-berry" when she means "library"
"frigerate" for "investigate"
I had a boyfriend - it might have been Hubby - finally hassle me that I say "umbrella" incorrectly, with four syllables instead of three - um-ber-ELL-a, instead of um-BRELL-a. It's kind of ingrained, and people seem to know what I'm talking about, so I usually don't worry about it. I have to consciously pronounce it correctly if I decide to. But I have become aware of it.
Why didn't my mother correct me? Because she says um-ber-ell-a too.