Outlook replies not loading on iphone

For the last month or so, my work email account has started playing up on my iPhone. Whenever I go to reply to an email, the likelihood is that it won’t let me - instead coming up with a perpetual ‘loading’ sign. This doesn’t happen with the account on my laptop, or with my iCloud email account. It’s also not consistent - about one time in ten, it will let me reply as normal. Any suggestions, please?