Webmail filtering isn't working properly

[#1]

In my webmail inbox (RoundCube) there are 12 dispersed emails from eBay (out of 87 emails in total) - I thought I'd put eBay into the search box to go through them quickly.
However only three entries were found when I hit return - and two of those were other emails sent by me containing eBay in the message body.
So why was only 1 out of the 12 emails picked up in the search? It's set to "entire message" with all boxes ticked.
Most of the emails are from ebay@ebay.co.uk - putting ebay@ebay.co.uk into the search box comes up with nothing at all!
Clearly something is deficient somewhere...

[#2]

45 views - no one expressing an opinion?

[#3]

Just tried again in a totally different context.
I searched on "cross" and only got one result despite knowing there should be more.
However note the header on the attached screenshot - it says it found SEVENTEEN emails yet is only displaying one.
Is the search routine permanently broken? Does no one else use it?
EDIT - XP/FF29.0.1

[#4]

Quote from: drj

In my webmail inbox (RoundCube) there are 12 dispersed emails from eBay (out of 87 emails in total) - I thought I'd put eBay into the search box to go through them quickly. However only three entries were found when I hit return - and two of those were other emails sent by me containing eBay in the message body. So why was only 1 out of the 12 emails picked up in the search? It's set to "entire message" with all boxes ticked. Most of the emails are from ebay@ebay.co.uk - putting ebay@ebay.co.uk into the search box comes up with nothing at all! Clearly something is deficient somewhere...

I've re-run the "ebay" search and found the same problem - eleven emails displayed but it says it's found 33!

[#5]

Sorry drj, can't really comment on this one as I'm not using RoundCube much and certainly never had the need to use the search filtering within it.
Anyway, not much help for you but I am following. 

[#6]

Oh, just had a thought, could the search be linked to page display? On the screen shots you've added unfortunately it doesn't show if pages are involved or not. So it might be possibly showing only the results on that particular page of emails you're viewing.
Should be quite easy to discount this idea, so I await your response.

[#7]

No - the count is currently showing 173 emails on one page -  when I did the screenshots it was about 130 or so but I've had a deluge of emails in from eBay in the last two days