Set-Content not working - powershell

Question

Basically, all that I'm trying to do is replace some text in a text file based on line number. In this example, only 2 out of 3 Set-Content actually work when I run the script. However, when I run the Set-Content that doesn't work with a breakpoint, or highlight the block and run it separately, it magically works. It also works if I remove the other two set-content blocks.
I've tried putting in multiple Start-Sleep, and have tried on Windows Server 2012 R2 and Windows 10, both with some version of PS 5. Get-Content is in parenthesis to ensure that that operation is complete before continuing. I've tried putting a Get-Content between each operation. The full script has multiple Set-Content in between the first and the last, and they all fail no matter which order they occur in.
You can test it yourself. Create a text file with this content:
;12.1 - MyName
$ScriptVer = "12.1"
If $VAR<"1.2.3"
Then run this:
#Declare Paths
$Temp = "\\FileShare\e$\Temp\file.txt"
#Get-Content
$KIXOLD = (Get-Content $Temp)
[decimal]$OLDVER = 12.1
$NEWVER = ($oldver + .1)
#Update Version Number in File - THIS WORKS
#I can put in multiple of these anywhere in the script and they all work
#I can even move this block to the end and it still works
$VerLine = Select-String -Pattern $oldver -Path $temp |
select -ExpandProperty LineNumber |
select -Index 1
$KIXOLD[$VerLine - 1] = "`$ScriptVer = `"$NEWVER`""
$KIXOLD | Set-Content $temp
#Find the old version in the text file and replace with new
#This FAILS unless there's a breakpoint or it's run separately
#It doesn't matter if it's the first set-content last, or middle, this fails
$CONV = $KIXOLD | where {$_ -like "*If `$VAR<`"1.2.3`""}
($kixold).Replace("$CONV", " If `$VAR<`"1.2.4`"") | Set-Content $Temp
#Update notes to contain current version - THIS WORKS
#I can put in multiple of these anywhere in the script and they all work
$linenum = Select-String -Pattern $oldver -Path $Temp |
select -ExpandProperty LineNumber |
select -Index 0
$NewLine = [int]$linenum +1
$KIXOLD[$linenum] = ";$NewVer - MyName"
$KIXOLD | Set-Content $temp
You'll find that the resulting text file looks like this:
;12.1 - MyName
;12.2 - MyName
$ScriptVer = "12.2"
If $VAR<"1.2.3"
when it should look like this:
;12.1 - MyName
;12.2 - MyName
$ScriptVer = "12.2"
If $VAR<"1.2.4"
To reiterate, the modification of If $VAR<"1.2.3" DOES occur if there is a breakpoint or if I run that selection separately.
No matter what I try, only the first and the last Set-Content work unless there's a breakpoint or it's run separately. I'm at a loss, any help would be appreciated.

Answer 1

.Replace method applied to an object does not change that object! Use
$CONV = $KIXOLD | where {$_ -like "*If `$VAR<`"1.2.3`""}
$KIXOLD = $kixold.Replace("$CONV", " If `$VAR<`"1.2.4`"")
$KIXOLD | Set-Content $Temp
or
$CONV = $KIXOLD | where {$_ -like "*If `$VAR<`"1.2.3`""}
($kixold.Replace("$CONV", " If `$VAR<`"1.2.4`"")) | Set-Content $Temp
$KIXOLD = (Get-Content $Temp)