Unstable test blend simple Q6

Test blend simple Q6 is unstable and produces different results in series of runs, since about version 6.9.1. I observe this quite regular on master since about January on my workstation (CPU i7-4790) using both VS 2010 and 2015. OCCT 7.0 also has this problem, while 6.9.1 - not, thus this bug is regression.

Error message is:
Error : The area of result shape is 1.62137e+08

Here is sample log of series of runs:

Draw[4]> test blend simple Q6
CASE blend simple Q6: FAILED (error)
Draw[5]> test blend simple Q6
CASE blend simple Q6: FAILED (error)
Draw[6]> test blend simple Q6
CASE blend simple Q6: FAILED (error)
Draw[7]> test blend simple Q6
CASE blend simple Q6: FAILED (error)
Draw[8]> test blend simple Q6
CASE blend simple Q6: FAILED (error)
Draw[9]> test blend simple Q6
CASE blend simple Q6: OK
Draw[10]> test blend simple Q6
CASE blend simple Q6: FAILED (error)
Draw[11]> test blend simple Q6
CASE blend simple Q6: OK
Draw[12]> test blend simple Q6
CASE blend simple Q6: FAILED (error)
Draw[13]> test blend simple Q6
CASE blend simple Q6: OK
Draw[14]> test blend simple Q6
CASE blend simple Q6: FAILED (error)
Draw[15]> test blend simple Q6
CASE blend simple Q6: FAILED (error)