FocusFusion [1] 1.4.0 update is now available in the Windows Store [2]. This version fixes two issues introduced with 1.3.7: the wavelet focus stacking being cropped too tight and small rendering artefacts.
There were also small performance improvements around memory management and caching for up to 10% faster fusion. This version also introduces the use of fused multiply-add [3] CPU instructions (FMA) whenever available, but a the moment with zero improvements unless you have very, very fast main memory.