Recent greps do not behave as documented with respect to after-context.  In the past I’ve been accustomed to –AX meaning print X lines of after context.  That is not how gnu grep is working now, but it is how it is documented.  In fact –AX, which I tested with a v3.4 that I build on Ubuntu 18, will print X+1 lines of after-context.  If you want 1, you must say –A0.