Loading a 1.12.2 structure block with signs on 1.20 removes the text

When loading a structure block saved in a previous version in 1.20, the text in the signs is lost.

Steps to Reproduce:

• Go on a 1.12.2 world

• Place a sign

• Write "Hello world"

• Save a structure block with this sign (or use the one attached)

• Go on a 1.20 world

• Load the structure block

Observed Results:

The sign does not have "Hello world" written on it.

Expected Results:

The sign has "Hello world" written on it.

Notes:

Loading a structure block created on a 1.20 world works as expected. The update from the old block entity data format to the new one is probably the cause.

Screenshots/Videos:

Loading the attached structure file created in 1.12.2 on 1.19.4/1.20