This is the same issue as MC-214650.

The bug

The "edge" texture is not used for glass panes where their edges don't connect to anything. This has the undesirable side effect of making them look almost invisible from the side.

Due to MCPE-31025, the edge texture for edges that are actually connected does not show up in some contexts.

How to reproduce

1. Place a glass pane
2. Make it connect to only one block
3. Observe

Expected results

The side of the glass pane opposite the connection would use the "edge" texture.

Actual results

It does not and ends up being very hard to see.