[122][default][128.german] Towboats for oil are not mixable/interchange able with others.

[Huperspace]

Towboats for oils are not mixable/interchange able with others
eg.: if you first select a towboat like "Schute Nr 9" you can't add Towboat "Geheimrat von Lavale" (until Dec 1925) and "Schluckspecht" (at 1929) same the other way around.
Except the newly fixed "Wilde Hilde" (at 1922) which i can mix with the "Schute Nr 9" towboats.

ps: in "Schute No. 9 Stahl" the "Stahl" should be changed into "Steel". if "Schute" is not it's proper name than change it into "Barge"(DE orginal: "Schute Nr. 9 Stahl")

[Roboron]

From pak128.german developer:

This is intended.
Due to the overlap in the usage time area between the tug and the tugboat, different generations of oil ships are allowed to be attached to the tugs.
I think, it is no need for mixing oil towboats

[Huperspace]

"Wilde Hilde" + "Schute No. 9" (working)
"Schute No. 9" + "Wilde Hilde" (working)
"Geheimrat von Lavale"/"Schluckspecht" + "Schute No. 9" (not working)
"Schute No. 9" + "Geheimrat von Lavale"/"Schluckspecht" (not working)
"Geheimrat von Lavale"/"Schluckspecht" + "Wilde Hilde" (not working)
"Wilde Hilde" + "Geheimrat von Lavale"/"Schluckspecht" (not working)
this is intended?