Powershell and ConvertTo-HTML

Puzzled by another issue with different outputs when running a script from Powershell ISE compared to a standard shell.

I am performing a number of SQL checks and formatting the resultset as an HTML fragment:

$html1 = $dataset1.Tables .......... ConvertTo-HTML -AS Table -fragment -PreContent '<h2>SQL Configuration</h2>' | Out-String

These fragments are then associated with variables covering each block of tests:

$svrconfig = $html1, $html2
$memory = $html3,$html4

The main body of HTML is defined as a variable (a$) containing div blocks for each of the variables listed above:

<div id+""Server Configuration"" class=""tabcontent"">" + $memory +"</div>

When running the final convert under ISE, a complete HTML document is produced with the variables in the div blocks being correctly substituted with the relevant HTML.

However, when executed under a standard Powershell shell with administrative rights, the final HTML conversion does not see the div variables being populated:

ConvertTo-HTML -body $a | Out-File -append $SQLStatusReport

As usual, any pointers gratefully received!

JC