Many direct entries on one specific landing page

We run a landing page that is advertised exclusively via Google Ads.
According to Google Ads, we had 263 clicks on the ad last week and according to Matomo, 218 visitors who can be clearly assigned to the campaign.
So that should be ok.

In addition, however, we have 854 direct entries in the same period, i.e. accesses without referrer. At first I thought of invalid clicks, which are filtered out by Google Ads, but there were only 18.
The visitors come from a wide variety of IP addresses, with different devices and operating systems, although there are noticeably many Android users among them. Most of these visitors have a duration of stay of 0 seconds.
Furthermore, it is striking that this enormous number of direct entries can only be found on this landing page.
Does anyone have an idea where these calls could come from? Are they bots? Or possibly a tracking error on the part of Google Ads or matomo?