Exactly.  However, this is completely lost on TurboTax.

For the error on the T3 slip not balancing box 52+53 to equal box 21A, trying to enter the sum of 52+53 into box 53 (deleting 52) should fix the problem.

We are aware of this issue, and our development team is working on a resolution. We appreciate your patience.

Thank you for choosing TurboTax.

I am experiencing the same issue.  It is not pulling the data from box 21 to form 936.  I do have boxes 52 and 53 completed on the T-slip, but the field on form 936 is zero.  As a result I am not able to submit the return using Netfile.  ETA on getting this resolved??

@CM1965 . Currently we don't have any ETA. Once it is resolved, we will update you in this thread. We appreciate your patience.

Thanks so much that worked for me as well

Is there a similar issue with capital gains in box 30 of T5013?

Is the T936 not picking up Box 21 issue fixed now?

Numerous forms do not pick up Box 21.  You have to take whatever amount is in Box 21 and ensure that the total of Box 52 + Box 53 = Box 21.  Since the capital gains inclusion rate is the same regardless of the time period (Box 52 or Box 53) the inclusion rate is still 50%. 

I have seveal T-slips with only Box 21's and no Box 52 or Box 53.  So, I just put the amount from Box 21 into box 53 and then the forms populate correctly.

TurboTax should have been able to code this all so that regardless of the Box 21, Box 52, and Box 53 configuration from the T-slip that the forms populate corectly, but they haven't ... at least not yet.