All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
What you have mentioned may be a cause of such difficult times. Also, the sins of some of the workers may be the cause. However, a Muslim should judge himself first, before judging others, especially when things begin to go wrong.
On the other hand, suspecting the resources of the Christian shareholder and surmising that they are from alcoholic drinks does not make it unlawful to enter a business agreement with him if the business activity is lawful. The Prophet, sallallaahu ‘alayhi wa sallam, used to trade with the Jews even though they earned their money by illicit means. Also, when the Prophet died, his armor had been pawned to a Jew. [Al-Bukhari]
The Prophet, sallallaahu ‘alayhi wa sallam, also answered an invitation to a meal from a Jew. [Al-Bukhari]
This only applies to the case if the shareholder you mentioned is not independently managing business transactions. It would be better if you could replace that partner, buy out his share, or dissolve your partnership with him.
Allaah Knows best.