I created a spreadsheet-doc with one data-sheet (mainly constants from a
database), some (hidden) sheets (looking up and  calculating things from the
first sheet in different ways) and there is a pretty formatted result sheet,
which shows some results from the hidden sheets. The results are linked to the
hidden calculations by arrays. So I have a sheet with some array-formulas
referring to  other sheets (more than one!). This is no problem until I add any
additional array-formula.
Before I lose myself in describing things, please reproduce the bug:
1. Create a new spreadsheet-document (sheet1, sheet2, sheet3)
2. Constant in sheet1.C1                sheet2
3. Constant in sheet1.C6                sheet3
4. Array-formula in sheet1.A2:E5        { =INDIRECT("$"&$C1&".$R$1:$V$4" }
5. Array-formula in sheet1.A7:E10       copied from A2:E5
Shows values of ranges R1:V4 from the sheets specified in C1 and C6.
6.Formula in sheet1.F1:         =SUMIF(G1:G9;">0")
7.Save and re-open the document and everything is fine.
8.Add an additional array-formula to sheet1.F2: { =SUM(G1:G9>0) }
9.Save and re-open.
The array-formula in A7:E10 is broken.

With this test-document I tried so far:
1."Hard coding" the sheet-names within the array-formulas:
A2:E5           { =$sheet2.$R$1:$V$4 }
and A7:E10      { =$sheet3.$R$1:$V$4 }
Without positive effect.
2.Changing the array-formulas to normal ones: =$sheet2.R1 copied to A2:E5 and
likewise with reference to sheet3:
This helps.
3.Using the additional array-formula  (F2) on some other sheet (also containing
arrays, but without references to other sheets):
Everything's fine
4.Omititng step 5, so there is only one array-reference to sheet2 and a second
array formula in F2:
This is no problem.
5.Using references to the same sheet within all arrays:
OK
6.Copy the array to the right side (to H2:L5 and to H6:L10) instead of downwards:
No problem.
My original document can do with solution 2., but I think it's worth to report
this bug.