As of 1.16, glass panes and walls now connect. This is a nice feature, but breaks builds that rely on the player's ability to fit in the space between a pane and a wall. It is also incredibly ugly when you use walls as columns or panes as railings, or both. As a general rule, panes should not connect on more than two horizontal sides unless connecting with other panes or solid blocks.

One solution might be to allow the player to shift right-click to place walls, panes, fences, and iron bars that do not connect. We could even go a step further and say that if you shift right-click in a horizontal direction it specifies that the face you are looking at won't connect, and if you shift right-click in a vertical direction it leaves all connections as "none" or "false" as the case may be.

Here is an example using one of my builds:

https://drive.google.com/file/d/1j3L5tSPBRpkG7G_dgVAl4y5rINX1Yq_L/view?usp=sharing

Before 1.16:

https://drive.google.com/file/d/1it7GAUds5PBHfl_2X5UNCF8vsmLbxRlb/view?usp=sharing

After 1.16:

https://drive.google.com/file/d/1j3BbbigEzvImDkgatZnevpVGGS8vy0fJ/view?usp=sharing

This can be fixed using the debug stick, however, no viable method currently exists to fix this issue in survival mode.