While trying to load pak128 form b.128.simutrans ... with the wrong version of pak128 (2.1.0 instead 2.2.0) I found out that the size of Erzbergwerk has changed between versions. Very bad. I would suggest in case of size changes rather a Erzbergwerk2 and an entry in the compat.tab, to avoid crashes. There will be then a missing factory, but the player is informed by this. The way a factory builder removes everything during loading will inevitely lead to crashes if another thing is missing (which was the case for 2.1->2.2 as all ways were redefiend).
Did you perhaps mean some other pakset? Erzbergwerk had dims=5,5 since 2007 (verified).
Other 128's factories that did change sizes even repeatedly were the sand pit and "deep" coal mine (can't remember exact names). But in these cases they became different objects and used compat.tab.
Ok, so maybe the game on b.128 is then completely screwed up, because it deletes a tunnel when building an Erzberwerk. Sorry, false alert on my side.
Well, that's one solved bug report then :)