Having the rendezvous radar on (so it was warmed up in case of an emergency landing abort) should have been irrelevant to the computer, but an electrical phasing mismatch between two parts of the rendezvous radar system could cause the stationary antenna to appear to the computer as dithering back and forth between two positions, depending upon how the hardware randomly powered up.
hˌævɪŋ ðə ɹˈɑːndɪvˌuː ɹˈeɪdɑːɹ ˌɔn sˌoʊ ɪt wʌz wˈɔːɹmd ˌʌp ɪn kˈeɪs əvən ɪmˈɜːdʒənsi lˈændɪŋ ɐbˈɔːɹt ʃˌʊdəv bˌɪn ɪɹˈɛlᵻvənt tə ðə kəmpjˈuːɾɚ, bˌʌt ɐn ᵻlˈɛktɹɪkəl fˈeɪzɪŋ mɪsmˈætʃ bᵻtwˌiːn tˈuː pˈɑːɹts ʌvðə ɹˈɑːndɪvˌuː ɹˈeɪdɑːɹ sˈɪstəm kʊd kˈɔːz ðə stˈeɪʃənˌɛɹi æntˈɛnə tʊ ɐpˈɪɹ tə ðə kəmpjˈuːɾɚɹ æz dˈɪðɚɹɪŋ bˈæk ænd fˈɔːɹθ bᵻtwˌiːn tˈuː pəzˈɪʃənz, dᵻpˈɛndɪŋ əpˌɑːn hˌaʊ ðə hˈɑːɹdwɛɹ ɹˈændəmli pˈaʊɚd ˈʌp.