I just installed my (v3) BL Touch with a vanilla version of Marlin (1.1.9) on my Ender 3 and everything seems to work fine (including auto home) except the probing. It repeatedly does the first three probes (successfully) but then tries the fourth and fails. Even when disabling the axis movement (X/Y stepper motors) the issue persists, which would indicate that it is not a bad connection or physical location dependent. Any ideas on how to troubleshoot?
On second thoughts, it seems that it now fails inconsistently, so it is probably a wiring issue, although there is still the issue of it not retracting before printing and not leveling well when it does (although those issues would be more appropriate for a separate question), among other things.