As a workaround it seems possible to limit the number of table classes used for a table to one class. Since head, alt1 and alt2 aren't really problematic to emulate, I think most tables could be rewritten manually if this persists longer.
This tables emulates how old tables can be created without using more than one class
though it increases the character count and is not as easy to change - which is certainly of concern for some threads using large tables.
Spoiler: CodeCode:[table="class:grid"] [tr] [th="bgcolor:#8E5A2E, align:center"][color=#FFFFFF][b]This tables emulates how old tables[/b][/color][/th] [th="bgcolor:#8E5A2E, align:center"][color=#FFFFFF][b]can[/b][/color][/th] [/tr] [tr] [td="bgcolor:#F0E7D3"]be created[/td] [td="bgcolor:#F0E7D3"]without using[/td] [/tr] [tr] [td="bgcolor:#DCCDAD"]more than[/td] [td="bgcolor:#DCCDAD"]one class[/td] [/tr] [/table]
(If it doesn't get fixed soonish, I will update my thread to acknowledge this problem.)