openHAB crash sometimes ( java.lang.OutOfMemoryError: Java heap space)

Platform information:
Hardware: Raspberry Pi 3 Model B
OS: Raspbian GNU/Linux 9 (stretch)
Java Runtime Environment: Java™ SE Runtime Environment (build 1.8.0_162-b12)
openHAB version: 2.4.0 Release Build

Hi, After 1/2/3/4 days (even after 1 hour) running I got in the logs this kind of warning in /var/log/openhab2/events.log:

2019-04-06 13:02:55.960 [WARN ] [me.core.internal.events.EventHandler] - Dispatching event to subscriber 'org.eclipse.smarthome.model.rule.runtime.internal.engine.RuleEngineImpl@132c0e7' takes more than 5000ms.
2019-04-06 13:04:53.371 [WARN ] [com.zaxxer.hikari.pool.HikariPool   ] - 2m43s131ms122μs918ns - Thread starvation or clock leap detected (housekeeper delta=yank-default).
2019-04-06 13:10:51.258 [WARN ] [com.zaxxer.hikari.pool.HikariPool   ] - 2m34s396ms149μs271ns - Thread starvation or clock leap detected (housekeeper delta=yank-default).
2019-04-06 13:22:50.219 [WARN ] [me.core.internal.events.EventHandler] - Dispatching event to subscriber 'org.openhab.core.events.internal.EventBridge@136de7' takes more than 5000ms.
2019-04-06 13:23:35.065 [WARN ] [org.eclipse.jetty.io.ManagedSelector] - java.lang.OutOfMemoryError: Java heap space
2019-04-06 13:23:00.572 [WARN ] [com.zaxxer.hikari.pool.HikariPool   ] - 12m36s405ms251μs517ns - Thread starvation or clock leap detected (housekeeper delta=yank-default).
2019-04-06 13:26:01.193 [WARN ] [me.core.internal.events.EventHandler] - Dispatching event to subscriber 'org.openhab.core.events.internal.EventBridge@136de7' takes more than 5000ms.
2019-04-06 13:26:02.360 [WARN ] [com.zaxxer.hikari.pool.HikariPool   ] - 4m18s616ms65μs508ns - Thread starvation or clock leap detected (housekeeper delta=yank-default).
2019-04-06 13:26:34.631 [WARN ] [com.zaxxer.hikari.pool.HikariPool   ] - 2m16s501ms839μs476ns - Thread starvation or clock leap detected (housekeeper delta=yank-default).
2019-04-06 13:30:42.548 [WARN ] [com.zaxxer.hikari.pool.HikariPool   ] - 4m2s150ms370μs504ns - Thread starvation or clock leap detected (housekeeper delta=yank-default).

Please help me to find issue.
Thanks.