Japanese grammar books say that ます-form should be used only at the very end of a (compound) statement. So 〜ないといけません。is a correct sentence ending. However googling "ませんといけない" finds lots of matches (348,000 vs. 482,000 for correct variant) which seem to be genuine sentences of native speakers, like
しかしながら明日からの仕事に向けて気持ちを切り替えませんといけないですね。
Is it a wide-spread colloquialism, or is ます-form actually allowed at each sub-statement end in a compound?