Goal seek Run-time 1004 error when using application.run from another Workbook - excel

Question

I have a run-time error that I can't solve despite having searched deeply into many forum.
Here is the problem: I am using a Macro in a Model looking for a optimal allocation through a Goal-Seek function.
When I use it within that model (let's call it Model 1), the macro works perfectly.
However, i need to work in that model and in another one, to get data that will fill a table located in a 3rd excel file, which is then my "main file" (let's call it Model 3).
Thus, I need to call that macro located in Model 1 via an Application.run from Model 3.
And when I do so, I get a "Run-time error '1004': Reference isn't valid." which relates to the Goal-seek function that I use in Model 1.
Furthermore, if after that I come back to Model 1 and try to use the macro, I get the exact same error message while it was working before.
Here are my codes:
Model 3 (main):
Sub Test_Optim()
Dim JFMPath As String
Dim MacroPath As String
JFMPath = Sheets("Inputs").Range("D2")
MacroPath = Sheets("Inputs").Range("A3")
Workbooks.Open JFMPath
Application.Run (MacroPath)
End Sub
Model 1:
Option Explicit
Option Base 1
Sub Optimization_Alloc()
'Definitions
Dim i As Integer
Dim k As Integer
Dim IRR As Single
Dim IRRDelta As Single
Dim vIRR() As Single
Dim MinIRR As Single
Dim vPPA() As Single
Dim PPALevel As Single
Dim MinPPA As Single
Dim Position As Integer
Dim FlipYearIterations As Integer
Dim IterTF As Boolean
Dim IterStep As Single
Dim FlipYear As Integer
Dim OptFlipYear As Integer
Dim vFlipYear() As Integer
Dim xDistribution As Single
Dim OptxDistribution As Single
Dim vXDistribution() As Single
'enables goal-seek iterations, MaxIterations is the number you would wanna change
IterTF = Application.Iteration = True
IterStep = Application.MaxIterations
With Application
.Iteration = True
.MaxIterations = 500
.MaxChange = 0.0001
End With
FlipYearIterations = 10
ReDim vPPA(FlipYearIterations) As Single
ReDim vFlipYear(FlipYearIterations) As Integer
ReDim vXDistribution(FlipYearIterations) As Single
ReDim vIRR(FlipYearIterations) As Single
For i = 1 To FlipYearIterations
vFlipYear(i) = 2027 + i - 1
Next i
'Loops through different FlipYears. For every year, optimal allocation of cash/tax is calculated by goalseek.
For k = 1 To FlipYearIterations
Worksheets("As_Yr").Cells(345, 9) = vFlipYear(k) 'Optimal flip year
Worksheets("As_Yr").Cells(350, 9).GoalSeek Goal:=0, ChangingCell:=Worksheets("As_Yr").Cells(346, 9)
'Here is the Goalseek function from which I get the run-time error
xDistribution = Worksheets("As_Yr").Cells(346, 9)
PPALevel = Worksheets("Cockpit & As_Gen").Cells(48, 9)
vXDistribution(k) = xDistribution
vPPA(k) = PPALevel
vIRR(k) = Worksheets("As_Yr").Cells(348, 9)
Next k
'Determines optimal FlipYear
MinIRR = WorksheetFunction.Max(vIRR)
Position = WorksheetFunction.Match(MinIRR, vIRR, False)
OptFlipYear = vFlipYear(Position)
OptxDistribution = vXDistribution(Position)
'Prints optimal setting to Excel
Worksheets("As_Yr").Cells(345, 9) = OptFlipYear 'Optimal flip year
Worksheets("As_Yr").Cells(346, 9) = OptxDistribution 'Optimal CF distrib
'restores to the original goal-seek iterations setting
IterTF = Application.Iteration = True
IterStep = Application.MaxIterations
With Application
.MaxIterations = IterStep
.Iteration = IterTF
.MaxChange = 0.001
End With
End Sub
Is this something that one of you could help me with?
I guess it is a dummy mistake, but I can't figure that out.
Many thanks,
Alice