@DaddyVader58 
I expiriencing the same issue for areas where wifi signal is not strong enough. Remember, wifi in light bulbs is not the best, and, as I mentioned in other post, kasa lights have better than average wifi in smart bulbs on the market.

@DaddyVader58 
all these 3 light bulbs in the same room in the same chandelier just few inches away from each other, but signal is so different, from great to average. 

and in the same room I can't keep light bulb connected inside metal one 

@MikeP 

I have tried that in the past as well.  So far, the only consistent remedy is to power cycle the affected bulb.  I have a Google WiFi Mesh (1 primary + 2 satellites).  None of the other TP-Link devices exhibit this issue, only the bulbs and only randomly.  

I use Home Assistant to tie all my home automation devices together.  I am going to create a Node-Red flow to query the bulbs every 5 minutes or so, to see if that a) keeps them connected by communicating with them, if this is due to some type of stand-by condition that they are stuck in and b) to send an alert when it happens, to try and determine any external cause.

Other than this issue, I am happy with these devices.  I can state that my Zigbee bulbs (Samsung Smartthings) never cause an issue but I only have 6 of those installed.  All my Zigbee devices (25+) have been trouble free.

I have this same issue as well. One or two bulbs or will randomly disconnect from wifi and become unavailable. They are all well blanketed with strong wifi signal. The only fix is to reset them and add them back to the app. Seems to happen regularly to specific bulbs. 

First check your router status to confirm that when the bulbs are offline they're actually disconnected from your wifi.

I don't have that model of bulbs (I have the LBs), but bulbs can struggle with wifi connectivity esp if there's any metal in the shade.

TP Link uses UDP locally which can be a problem for some routers. Try rebooting the router when it happens, if it goes away it's the router.

Static IP doesn't help. Connecting your phone locally might not help either, depends on your network. You could try temporarily blocking them at your router to see if they switch to "local only" and see if they still drop - narrows it down to your local network vs your ISP or TP Link.