So, I have two ceiling lights in my living room - both connected via the same switch. Last week, I installed one Smart Bulb (the LB110 model) that I had had in my cupboard for many months! I was happy with the smooth installation and the way it works with Alexa, so purchased another Kasa Smart Bulb (the KL50 model) for the second light. This time, I could not complete the installation (it wouldn't 'blink') despite following the various suggestions by customer service. However, it did successfully install in my hallway! Therefore, the consensus is that it is the light fitting that is at fault - I tested this by moving the pre-installed Smart Bulb to the 2nd location and - hey presto - it wouldn't work, and nor would a 'normal' bulb.
This is a long-winded way of asking....has anyone come across issues where installing one Smart Bulb can cause the failure of a 2nd electric light fitment on the same switch?