This issue is fixed in PCS OS 8.2R3 and up.
For versions other than 8.2R3 and up a rewriter filter (filter58152.pkg.encrypted) is available that will filter rewriting for the URL *:*/*microsoft.owa.core.controls.editorbase.js and provide the same fix.
To obtain this filter open a support case with Pulse Secure Global Support Center and provide the filter ID needed.
The following workaround can also be implemented as an alternative to the above solutions:
- Disable Automatic Signatures in OWA/Exchange
- Configure the Reading Pane options to open new e-mails in the same windows in OWA/Exchange