Can not open imported lesson : Something went wrong Cannot read properties of undefined (reading 'get')

I try to impor some lessons but when I click the newly import lesson it will always get error

Something went wrong

Cannot read properties of undefined (reading ‘get’)

this is lesson link
en/learn/ja/web/reader/23135935

but I can play it from view course link

the only less I can open is I switch the CC to auto translate from English to Japanese which will be very incorrect to use

Thanks for reporting. We will investigate the issue.

Might be different in your case, but I’ve experienced this a few times, but it turned out to be just due to internet-speed issues for me.