The increased floating point precision in QlikView 11.20 SR5 (and later) does not make calculations incorrect. It is likely that the previously observed result is also not exactly accurate compared to the source data, which is in line with the nature and expectation of using floating point values for decimal value representation.
If the result is not inline with expectations, there are several techniques to improve the value precision
NOTE: The floating point precision can be improved, but a decimal value in QlikView should never be assumed as exact. There can always be a variation on the last decimal value.
In logical comparison the result can differ if one of the compared values is unexpected due to the increased precision. For this scenario please see the following example applied in timestamps.
The easiest way is to compare the actual timestamp text instead of the underlying decimal value. This can be done by using the Text() function.
QlikView is optimized for processing of numerical values, so the text comparison could possibly give a negative performance impact on large data quantities with many distinct values. In such case it could be better to try and perform the comparison with integer values. This can be done by multiplying the decimal value and thereafter using Floor() to remove the decimal part of the value.