I'm checking for a stability problem of QGIS 2.18 grass algorithms. I could not use Grass algorithms like r.reclass with QGIS 2.18.4 (64 bits) After researching in forums and using all the recommendations without success, I ended up performing the advanced installation with OSgeo4W. It worked! Only less than 2 weeks later, the error messages when using the algorithm again, have returned! This shows the instability of the software. Has anyone had this and have a suggestion?
Try to download QGIS 2.14.12 Long Term Release (LTR) from OSGeo4W instead of QGIS 2.18.4. QGIS 2.14.12 LTR is more stable than QGIS 2.18.4 as the latter is still under development and regular bugs fixes. Personally, I always use QGIS LTR for my daily work rather than QGIS 2.18.4. However, this does not guarantee that your problem will be fixed as we still do not have enough information from you.