Belt/Chain mate error

Hello,

i'm drawing an engine but, when i try to connect the Camgears, crankshaft and belt tentioner with the Belt/Chain feature, a lot of mates become yellow errors. Does anyone know what causes it to do that? i wanted to know what was wrong so i deleted all the mates and looked what would happen (ofcourse i did not save after deleting it all). and the whole engine block (the light blue part) just disapeared.

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