My Sim on Sims 3 glitched without me doing anything?

i downloaded a guy from the Sims 3 exchange, and it said it filled in the missing stuff with these things called "proxies" ( i have no idea what those are)... so i started playing Sims 3 and he got married and then i made them have twins. i aged one up and had a birthday for it normally, then i taught it to walk and then i took it up stairs and put it in its panda crib... then it happened, my sim baby boy glitched its arms were all loopy and could not tell they were arms and they were HUGE and pointy like. all that was in the crib was its head and half of it's cheast and its legs, you could see right through it middle so i got freaked out and saved and quit... and the girl Sim ( the one that got married) i made her with the sims 3 creator i started with her then added him on the game... feel free to ask stuff i might have left out that you were wondering about... i'll answer back quick!! THX for reading.... and how do i fix this sims toddler problem?