Select File button has stopped working, with JS errors

Hi,
The “Select File” button no longer puts the name of the selected file into the filename_1 text input field. Turning off Ajax did not help. Enabling debug mode did not help.

I upgraded WordPress to 4.9.4, and various plugins, 3 days ago.

The Chrome console shows lots of JS errors from the wp-file-upload scripts. The first few are:

Uncaught SyntaxError: Invalid or unexpected token (index):153
(index):185 Uncaught TypeError: Cannot set property ‘visualeditorbutton’ of undefined
at WFU_JS_1_visualeditorbutton ((index):185)
at wfu_run_js ((index):110)
at (index):189
WFU_JS_1_visualeditorbutton @ (index):185
wfu_run_js @ (index):110
(anonymous) @ (index):189
wordpress_file_upload_functions.js?ver=4.9.4:2 Uncaught TypeError: Cannot read property ‘title’ of undefined
at wfu_js_decode_obj (wordpress_file_upload_functions.js?ver=4.9.4:2)
at wfu_run_js ((index):110)
at (index):212

(There are more but I think the root cause is the first error)

Line 152 is:
else{document.getElementById(‘wfu_messageblock_arrow_1’).style.display=”none”;header_container.colSpan=3}}
Line 153 starts with:
var next_block=document.getElementById(‘wfu_messageblock_subheader_1’);var next_block_id=0;var file_block=null;

Thanks in advance,

Steve

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