Describe the bug

The Speed Control Buttons are not initially visible on screen. Hitting F5 will make them appear but if you hit F5 again, they disappear again.

I'm just looking for some assistance in debugging this problem. There are no obvious error messages written to the console.

The Context

• WordPress Version WordPress 5.9.1
• Other plugins
  Numerous:

Advanced Custom Fields
Advanced Editor Tools
Classic Editor
Client Portal
Custom Error Pages
Duplicator
Form Maker
GDPR/CCPA Cookie Consent Banner
HTTP headers to improve web site security
Inactive Logout
Insert Headers and Footers
Insert PHP Code Snippet
jQuery Updater
Limit log in attempts reloaded
Lock User Account
Media Playback Speed
Minimum Password Strength
PDF Embedder Premium Secure
Popup Maker
Profile Builder
Remove Admin Toolbar
Simple Custom CSS and JS
Simple prevent users sharing sign-in information.
Simple User Meta Editor
Theme Check
TinyMCE Spellcheck
TLS 1.2 Compatibility Test
UpdraftPlus - Backup/Restore
User Login History
User Meta Lite
User Role Editor
Who's Logged In
Wordpress File Upload Pro
WP Better Emails
WP Content Security Policy Plugin
WP Maintenance Mode

• Theme
  running Twenty Seventeen Child theme.

• URL that we can verify and gather more info from (please do not include usernames or passwords)
  Can't do this, as it is password protected.

Screenshots

Screenshots attached, along with source code and rendered html.

Preview Assigned Translation screen.pdf
Desktop (please complete the following information):

• OS: Windows 10 Pro 10.0.19044
• Browser: Firefox 97.0.2 and Opera 84

Smartphone (please complete the following information):

N/A

Additional context

this is not a show-stopper, but I wondered if you had encountered anything like this before and could give any advice on what to look for.