The British Ministry of Defence wrote about this on Twitter.
British intelligence notes that since the beginning of May 2023, Russia has been increasingly losing the initiative in the war against Ukraine, rather than advancing its own military goals.
"During May 2023, Russia has launched 20 nights of one-way-attack uncrewed aerial vehicle and cruise missile attacks deep inside Ukraine. Russia has had little success in its likely aims of neutralising Ukraine’s improved air defences and destroying Ukrainian counter-attack forces. On the ground, it has redeployed security forces to react to partisan attacks inside western Russia," British military analysts said.
They assume that Russian commanders are trying to accumulate reserve forces and deploy them where they believe a Ukrainian counterattack will take place. However, this task is complicated by the need to fill in the gaps on the front line around Bakhmut.