halacha - Mincha started before sheki'a, extended beyond it. What about davenning maariv straight after mincha?

A minyan starts to daven mincha before sheki’a with the intention to daven maariv after sheki’a. In the event, mincha extends beyond shki’a.

There are IMHO three possible cases:

1. 
   

   They start but do not finish the quiet shmoneh esrai before shki’a.

   
   


2. 
   

   They finish the quiet shmoneh esrai but not the repetition.

   
   
   


3. 
   

   They finish the repetition but don’t finish the rest of davenning.

   
   

Is any of these situations “tartei desasrei” – two contradictory acts?

This question is related to but not identical to When is the earliest time you can Daven Maariv during the week?.

Answer

This answer presumes that the minyan is davening back-to-back because otherwise people may go home and end up not davening maariv. Therefore, I am bringing a psak that not everyone agrees to, but may be applicable under the aforementioned circumstance- CYLOR.

The Aruch haShulchan (OC 110:5) holds that one who starts davening in the proper time is davening "on time" regardless of when he finishes.

He learns this from Tosafos on Brachos 7a. There is a drasha showing G-d's kindness for not getting angry during Bilam's curse. Since G-d's anger is only a split second (see gemara), Tos. asks what Bilam could have accomplished? One of his answers is that he could have started the curse and it would have retained it's potency afterward.

The only thing I'm not sure about is the shatz for mincha who davened the total repetition after sunset, since I recall (not sure where) that the repetition is his actual tefila and his silent one was a rehearsal (established pre-siddurim). So his entire tefilah may have been post-sunset.